[BUG] Inconsistent validations about the ledger

[dhythm]

Describe the bug
An empty footer could be registered as a ledger template.
However, the ledger history API (GET /[domain}/[token_address}/history/{ledger_id}) will be failed to get the ledger with empty footer after the registration.

Expected behavior
An error doesn't happen and data should be returned.

Additional context
It could be better for the validation,

• each header (ledger and details) doesn't allow empty input because there is the title / heading item on top of the header
• each footer (ledger and details) allows empty input because the footer is isolated item.

[YoshihitoAso]

Thank you for your feedback.

The inconsistency of the null constraint in the system is a bug, which we will fix.

Regarding your suggestion that the header should be non-null, this feature is built to be used for general purpose ledgers, so it is possible for a ledger to not have a header.
Therefore, we think it is right to design the header to allow null.

[dhythm]

Thank you for your reply and your idea is understood for me.
I will reconsider whether add the validation for the header at our frontend service or not.

Anyway, I'm waiting for fixing the bug. Thx 👍