Return all invalid alternative hosts at once in a structured way

When creating or updating a meeting with one or more invalid alternative hosts, only one invalid user is returned at a time. The user is returned in at least two different undocumented error messages (with different error codes) that need parsing.

Using POST /users/{userId}/meetings and PATCH /meetings/{meetingId}

Describe the solution you’d like
It would be nice to have all invalid alt-hosts at once in a structured way. For example:

invalid-alt-hosts: ["a@aa.a", "b@bb.b"]

Ideally also a flag that would allow to create the meeting aniway without the invalid alt-hosts.