v0.38.1

A clearer answer when an account already has its business logo.

One business logo per account

Google allows one business logo at account level. A second one used to pass the draft and then fail at the dry run with a bare RESOURCE_LIMIT error (ENABLED_FAVICON_ASSET_LINKS_PER_CUSTOMER). We found this while testing 0.38.0's account-level logos on a live account.

• At the draft: draft_image_assets with scope="account" and link_asset_to_customer now check for a logo already linked to the account. If there is one, the draft is refused, and the message names the logo and the exact remove_entity call that frees the slot.
• Several logos at once: a draft that would link more than one business logo to the account is refused straight away.
• Campaigns are unchanged: a campaign accepted a second logo in the same test, so campaign-level logos aren't checked.