Add validation to select either topic or tag in Recent Blog Entries

[AdalbertoMoz]

Description

The following changes attend two validations related to the recent_blog_entries.py file:

• A Tag or a Topic must be selected; otherwise, raise an error.
• If both Tag and Topic are selected, raise an error as well.

Also, some improvement-changes were made to improve readability.

Link to sample test page: https://foundation-s-feature-88-ev6doo.herokuapp.com/
Related PRs/issues: #8832

To Test

1. Go to the Review App Blog Index Page

2. Try to add a Recent Blog Entry, for example, inside the Mozilla Festival Page (inside of the Body)
   

3. Try to save the document in the following scenarios:

   Condition	Error Message
   Neither Tag nor Topic is selected	Raise a required error
   Both Tag and Topic are selected	Raise an invalid error
   Only one is selected	No errors, show the filtered blogs

Required error:

Invalid error:

Checklist

Tests
- [ ] Is the code I'm adding covered by tests?

Changes in Models:
- [ ] Did I update or add new fake data?
- [ ] Did I squash my migration?
- [ ] Are my changes backward-compatible. If not, did I schedule a deploy with the rest of the team?

Documentation:
- [ ] Is my code documented?
- [ ] Did I update the READMEs or wagtail documentation?

Merge Method
💡❗Remember to use squash merge when merging non-feature branches into main

┆Issue is synchronized with this Jira Story

[danielfmiranda]

Amazing work! LGTM 🚀

[data-sync-user]

➤ Simon Acosta Torres commented:

PR has been merged.