ORM defaults and integration test

[MaximeBICMTL]

Description

This PR adds default values to the ORM columns based on the values specified in the LORIS SQL schema.

The default values are added to the Python side, which has two advantages:

• First, this allows to use the decorators specified in the models (example: use True instead of "Y")
• Second, this allows to use the field values directly upon model object construction, rather than after flushing to the database. This also allows to have better typing down the line (since fields are always populated, they do not need to be nullable).

Changes

This PR contains three changes:

1. Improve the test_orm_sql_sync.py integration test to compare ORM defaults to those of the LORIS SQL schema (non-trivial since ORM defaults are compared to SQL ones).
2. Update the ORM models using the updated integration test.
3. Remove some initialization values that were specified manually in the code but are no longer needed since they are now specified as default.

Note

Note that the actual default values are very often bad and potentially harmful IMO, but this would need to be corrected in the LORIS SQL schema rather than in this PR.