Acceptance criteria:

• Current messages it will replace:

all current errors where the read-only element would be modified (except PATCHing)
E.g. Changing property id of statement for all endpoints (except PATCH, see T366255) where this occurs

• HTTP status code: 400
• Error code: "cannot-modify-read-only-value"
• Error context: { "path": "{readonly_value_pointer}" }
• Error message: The input value cannot be modified