2714 custom fields

[iamleeg]

This is the first part of extending the model in the data service with additional fields: adding those fields and storing descriptions in the DB. Still to come:

• replay the stored fields on launch
• watch the DB for new fields being added (so multiple instances of data-service can stay in sync)
• integration tests to ensure that the case controller works with the updated fields correctly
• remove fields
• add fields that are lists of values
• number types
• validation
• fields that are enumerations (with optional "other" free text entry)
• indicate that a field is required (with a default value for migrating existing documents)
• can GET the data dictionary

[jim-sheldon]

except ConflictError returns 409, except PreconditionUnsatisfiedError returns 400,
and except KeyError returns 400?

[iamleeg]

so KeyError shouldn't happen: that will come from Field.model_type if you try to use a field type that isn't in the allowed list. So we turn it into PreconditionUnsatisfiedError which is the same as when we explicitly check that the type isn't found in the allowed list: i.e. both exception paths mean the same thing so they result in the same error (400 bad request: you've asked for something we aren't going to let you do).

ConflictError does indeed result in a 409 Conflict status.