Indicator processor: do not reprocess the same period when application restart

[benoit74]

Rationale

Fix #97

Changes

• in indicator processor, detect if we have already processed the last period found in DB and act accordingly
• I have "augmented" the test_restore_from_db_start_new_period_not_recorded test to exercise the "usual" condition where we have not yet recorded the last period found in DB at application restart (test is GREEN even without code changes)
• I have add the test_restore_from_db_start_new_period_recorded test to exercise the "rare" condition where we have already recorded the last period found in DB at application restart (test is RED without the code changes)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (824f8b5) 100.00% compared to head (692f69b) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #98 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 37 37 Lines 1092 1100 +8 Branches 202 204 +2 ========================================= + Hits 1092 1100 +8 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.