[ads] Implement common `HTTP_UPGRADE_REQUIRED` response code business logic

[tmancey]

List of endpoints which need considering for this change:

• [ ] catalog

• [ ] issuers

Geographic subdivision:

• [ ] get subdivision (aka get state)

Refill confirmation tokens:

• [ ] request signed tokens
• [ ] get signed tokens

Redeem confirmation token:

• [ ] create confirmation
• [ ] fetch payment token

Redeem payment tokens:

• [ ] redeem payment tokens