Add suspended field

Problem/Motivation

Theoretically it makes sense someday to have a 'suspended' field that allows staff to suspend a declaration (e.g. pending manual review) - so it's not used to make claims - but doesn't impugn the validity of past claims.

Nothing depends on this architecturally, it can safely be postponed.

Proposed resolution

- add a 'suspended' boolean to the declaration entity.
- add an isSuspended() getter to the declaration entity
- suspended declarations should not be:
-- claimable
-- ongoing
-- queued for confirmation
-- sent confirmations

Remaining tasks

User interface changes

API changes

Data model changes