books: All tools use books.Loader.dispatch() and LoadResult.

This is significant code deduplication, as seen in the diffstat.

tests: Test updates for accrual report changes in the last commit.

Where assertions are removed from individual tests, I believe that
functionality is covered by other tests (although probably not to the extent
of checking multiple splits).

cliutil: Add ReturnFlag.

Take this opportunity to re-standardize flag values now that it's clear
what's most common.

accrual: Restore "since last nonzero" behavior to outgoing report.

Basically this behavior is an extension of the fact that the outgoing report
is grouped by RT ticket rather than "accrual data." Ripping this
functionality out of other reports was correct, but it needed to stay for
the outgoing report.

accruals: Aging report shows all unpaid accruals color coded by age.

Some readers care about recent accruals, some don't. This presentation
accommmodates both audiences, providing the data while making it easy to
ignore or filter out recent accruals.

accrual: Rip out unnecessary functionality.

Now that make_consistent is really robust, there's much less need to do all
the consistency checking that was done in AccrualPostings.__init__. I expect
this will provide a performance benefit for large reports, since we'll be
calculating data for many fewer accrual groups. The only performance penalty
I see is that the aging report has to calculate the balance three times for
each row it reports, twice in write() and once in write_row(), but that
seems okay and can be cached separately if needed.

accrual: AccrualPostings.make_consistent() groups accruals by date.

This accommodates cases of contracts without separate invoices,
where a series of payments are scheduled over time.

The dance we used to do of group-by-invoice, then make consistent was
already suspect. It was originally motivated by the consistency checks that
are now gone. Use this opportunity to clean up and just make make_consistent
a classmethod.

accrual: Generate an aging report in more cases.

Default to generating an aging report unless the user searched for a
specific RT ticket or invoice.

cliutil: Add make_entry_point() function.

This provides better logging setup, reduces the amount of boilerplate in
main, and replaces is_main_script().

accrual: Actually use RT caching as intended.

Basically none of the reports were reading or writing the RT link cache
because they didn't instantiate an rtutil.RT properly to do that.

accrual: Add AccrualPostings.rt_id property.

This is like the existing attributes, but it only supports the outgoings
report, so don't build it at __init__ time.

accrual: Remove the consistency checker.

Everything it said was a problem has been done legitimately in our books at
one point or another.

* Variation in contract can happen in different line items of an invoice or
"group of contractor" situations.

* Variation in cost can happen because one invoice spans a period of time,
like donation matching programs. There is probably still value in a tool
that checks to make sure we use consistent rates each day, but that
affects all kinds of transactions, not just accruals, so it would be
done better in a separate tool.

* Variation in account happens because invoices legitimately span accrual
accounts, like donation matching programs with fees payable.

So: it's gone, good riddance.

accrual: Add columns to the aging report. RT#11439.

This adds almost all the metadata that's relevant to accruals.
I considered adding statement, but that cuased rows to get spaced out a lot,
and statement's kind of a low-value column, so I decided against it.

Ultimately I would like to make this configurable but that's for the
future.

accrual: More detailed text for "total aged" lines in aging report.

Per bkuhn's request.

accrual: Aging report uses group since last nonzero. RT#11600.

This makes it consistent with our other reports. The fact that it wasn't
already was basically an oversight.

cliutil: Add generalized SearchTerm class.

This makes the same filtering easily available to other reporting tools for
consistency.

accrual: Make accruals consistent by entity on the accrual side.

It is more common than I realized that we split an invoice by
entity on the accrual side, so this supports that better.

It still disregards inconsistency between accrual entity and payment entity
for reporting purposes, to help keep reporting clean around automatic
imports.

The changes to BaseReport._report shook out because at this point, the group
key is effectively arbitrary and shouldn't be used for any reporting
purposes.

accruals: AccrualPostings only reports inconsistent cost per currency.

Of course if an accrual has multiple currencies, it'll probably have
different costs, and that's fine.

accrual: Filter opening balance txn before main reporting.

So far we've been implicitly relying on this by the user passing search
terms that filter out the opening balance transaction. That will stop
happening with the aging report, so we need to do it ourselves.

accrual: Add AccrualPostings.make_consistent() method.

This will help the aging report better render dirty data.

reports: Make RelatedPostings an immutable data structure.

This was an early mistake, it makes data consistency mistakes too
easy, and I only used it once so far in actual code. Going to fix
this now so I can more safely build on top of this data structure.

tests: Add test for trying to make outgoing report without rt-id.

Changes to other test cases are to make them *not* trip up this
error after adding it to the books.

accrual: Refactor reports into classes.

Preparation for introducing the aging report. This helps us
distinguish each report's setup requirements (different __init__ arguments).

tests: Refactor accrual tests.

Preparation for adding the aging report.

reports.accrual: Exclude payments from default output. RT#11294.

This makes the output more useful for broad searches like on an
entity. Invoices that cross FY boundaries will appear to be paid
without being accrued, and so would appear when we were just
filtering zeroed-out invoices.

If we integrate the aging report into this module in the future,
that'll need to follow different logic, and just filter out
zeroed-out invoices. But the basic balance report and outgoing
report are more workaday tools, where more filtering makes them
more useful.

tests: Generate configuration in accrual-report tests.

Usually reduces the amount of testing boilerplate.

accrual: Outgoing report doesn't put RT web links in < >.

The RT web interface doesn't handle angle brackets well, making the
`>` part of the link.

books.Loader: New loading strategy.

The old loading strategy didn't load options, which yielded some
spurious errors. It also created awkward duplication of plugin
information in the code as well as the books.

Implement a new loading strategy that works by reading one of the
"main files" under the books/ subdirectory and includes entries
for additional FYs beyond that.

This is still not ideal in a lot of ways. In particular, Beancount can't
cache any results, causing any load to be slower than it theoretically could
be. I expect more commits to follow. But some of them might require
restructuring the books, and that should happen separately.

reports.accrual: Begin reporting.

This module basically reimplements the old payment-report+income-report,
in a single tool (after setting aside some of the checks that have moved
to the plugin). The aging report can be implemented here too when we need
that.