having `/invite/service/<token>` and `/invite/service/<id>` as two
separate routes (the first to validate an invite token, the second to
retrieve invite metadata) technically works. Routes are matched from
first to last until a match is found. The metadata endpoint only accepts
UUIDs, so requests with a UUID will be picked up by the correct
endpoint, while requests that don't look like a UUID will carry on
searching for an endpoint, and will find the token validation endpoint.
So while this works correctly for our normal expected input, it only
does so _because the UUID endpoint is first in the file_. This isn't
great, and it makes it harder to reason about the URLs when looking at
them.
To solve this, create the new `invite/service/check/<token>` endpoint.
For backwards compatibility, assign this in parallel with the existing
route - once the admin uses the new route we can remove the old route
and make better guarantees about what endpoint is being hit.
nb: the routes are not changing as part of this, only file paths and
blueprint names.
invite -> service_invite
this blueprint handles fetching invites for a service, creating invites,
etc.
accept_invite -> global_invite
this blueprint handles accepting invites for now, but will also involve
retrieving service/org user invite data without knowing the service/org
id associated. i'm not in love with this name and open to suggestions,
but i wanted to contrast it from service_invite and
organisation/invite_rest.py.
