7.10Error categories are more useful

For an integration API, think:

BAD INPUT
→ 400

NOT FOUND
→ 404

AUTHORIZATION
→ 401 / 403

CONFLICT / business rule
→ 409 / 422 depending on contract

DOWNSTREAM TEMPORARY FAILURE
→ 502 / 503 / 504

UNEXPECTED BUG
→ 500

Your API shouldn't expose:

SALESFORCE:INVALID_INPUT

directly to consumers.

That's implementation detail.