Determine how to standardize external entity statements vs internally provided entity statements

[rs59]

Consider:

• Decoding external entity statements to provide them internally (stored as Entity Statement) in the database (advantages: easier to make a flexible data format, it is also unlikely that the internal DB contents will be changed without first having the external ES changed first; disadvantages: less rigorous checks on data format, potential mismatch between internal and external entity statements). Might want to run a DB integrity check on startup or an ES validator if sent by issuers and/or have a view on the DB which can be used to visualize all contents.
• Encoding database columns to provide them externally (advantages: easier visualization of data; disadvantages: hardcoded format in database can make it harder to upgrade DB, slower)

Middle ground:

• Store signatures in DB and run pre-check to confirm signature accuracy; store JWKs as a string to avoid specific keys being used; run DB pre-check