global: add support for index templates

[zzacharo]

❤️ Thank you for your contribution!

Description

Please describe briefly your pull request.

Checklist

Ticks in all boxes and 🟢 on all GitHub actions status checks are required to merge:

• I'm aware of the code of conduct.
• I've created logical separate commits and followed the commit message format.
• I've added relevant test cases.
• I've added relevant documentation.
• I've marked translation strings.
• I've identified the copyright holder(s) and updated copyright headers for touched files (>15 lines contributions).
• I've NOT included third-party code (copy/pasted source code or new dependencies).
  • If you have added third-party code (copy/pasted or new dependencies), please reach out to an architect.

Frontend

• I've followed the CSS/JS and React guidelines.
• I've followed the web accessibility guidelines.
• I've followed the user interface guidelines.

Reminder

By using GitHub, you have already agreed to the GitHub’s Terms of Service including that:

1. You license your contribution under the same terms as the current repository’s license.
2. You agree that you have the right to license your contribution under the current repository’s license.

[kpsherva]

these functions look a bit too similar and I am worried they will be easily confusing, but I don't have a good idea on how to avoid this. Maybe a bit more elaborate comments on both to explain the backwards compatibility of register_templates vs register_index_templates?
also I guess, we cannot raise errors instead of empty list, because we lose the backwards compatibility ?

[kpsherva]

any way of installing one or the other, not both? maybe we need to deprecate invenio_search.templates?

[zzacharo]

After discussing with @slint IRL, we decided to drop the deprecation warning and add it only when we have a documented upgrade path.

[slint]

I'm not sure if it makes sense to show a deprecation warning without having a "way out". Usually these warnings link to some documentation that explains why the change is happening and how to migrate to the new solution (see example below).

I think to move things forward it would be better to cut a minor release, and include this deprecation warning in a new PR that would also include this extra information in the text (and release as a minor/patch).

---

GH Actions deprecation warning

SQLAlchemy

SADeprecationWarning: When transforming <class '__main__.User'> to a
dataclass, attribute(s) "create_user", "update_user" originates from
superclass <class
'__main__.Mixin'>, which is not a dataclass. This usage is deprecated and
will raise an error in SQLAlchemy 2.1. When declaring SQLAlchemy
Declarative Dataclasses, ensure that all mixin classes and other
superclasses which include attributes are also a subclass of
MappedAsDataclass.