[i18n] Save preferred_language for auth user in db

[rajatvijay]

Relates #2927

Technical details

This PR does the following things -

1. Adds Locale middleware in BE
2. Add a preferred_language attribute in the users model and serializers. Migrations for this field.
3. Adds the Preferred Language dropdown in the user's profile page.
4. Load the changed preferred language's translations from the profile page dynamically, on the client side.

Screenshots

users_lang_in_db.mp4

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
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• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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[rajatvijay]

@ghislaineguerin @kgodey assigned you for a product related review.

[ghislaineguerin]

@rajatvijay Looks good to me.

[kgodey]

Could we name the option "UI Language" or "Display Language"? I think that's clearer than "Preferred Language". I'd also update the backend name to match.

Otherwise, looks good.

[seancolsen]

"Preferred Language" and "Display Language" both seem fine to me. But "UI Language" seems like is has the potential to confuse some people who are not familiar with that acronym.

[kgodey]

Let's do "Display Language" then.

[silentninja]

I reviewed the changes to the backend code and it looks good to me!

[seancolsen]

I've noted a couple small comments on the diff, but a larger issue here is that we'll need to find a way to hide this UI before we can merge it. Otherwise we should hold off on merging until we have the full Japanese translation available.

[rajatvijay]

Commented out the Display Language select on the profile page 36d314d

[seancolsen]

Looks good now 👍🏻

[seancolsen]

I'm holding off merge since this is stacked on top of #3102. @rajatvijay feel free to merge this yourself once that PR is merged.

[seancolsen]

I'm trying to move this PR along in order to reduce our PR backlog so I spent some time resolving git merge conflicts in several files. Even though I'm not familiar with the code changes in this PR, the git conflicts seemed straightforward enough that I resolved them in c0b6cb3.

However, when I try to run Mathesar after that commit, the service container prints:

django.core.management.base.CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0005_user_display_language, 0008_auto_20230921_1834 in mathesar).
mathesar_service_dev | To fix them run 'python manage.py makemigrations --merge'

In an attempt to fix this problem, I ran the following command:

sudo docker exec mathesar_service_dev sh -c "python manage.py makemigrations --merge"

That gave me this output, which seems quite strange:

Merging mathesar
  Branch 0008_auto_20230921_1834
    - Add field sheet_name to datafile
    - Remove field sheet_name from datafile
    - Add field sheet_index to datafile
    - Raw SQL operation
    - Add field db_name to database
    - Add field editable to database
    - Add field host to database
    - Add field password to database
    - Add field port to database
    - Add field username to database
  Branch 0005_user_display_language
    - Add field display_language to user

Merging will only work if the operations printed above do not conflict
with each other (working on different fields or models)
Do you want to merge these migration branches? [y/N] Traceback (most recent call last):
  File "/code/manage.py", line 22, in <module>
    main()
  File "/code/manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.9/site-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 371, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 85, in wrapped
    res = handle_func(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/commands/makemigrations.py", line 133, in handle
    return self.handle_merge(loader, conflicts)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/commands/makemigrations.py", line 276, in handle_merge
    if questioner.ask_merge(app_label):
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/questioner.py", line 200, in ask_merge
    return self._boolean_input(
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/questioner.py", line 87, in _boolean_input
    result = input("%s " % question)
EOFError: EOF when reading a line

Aside from the "Conflicting migrations detected" message, Mathesar appears to function normally.

I would like a back-end engineer to look into this.

[seancolsen]

I figured it out — it was an issue with accepting user input when using docker exec. I was able to generate a new migration by running:

sudo docker exec mathesar_service_dev sh -c "python manage.py makemigrations --merge --no-input"

I committed that migration in 825a36f

[seancolsen]

If all the tests pass, I'm assuming we're good to go here, so I've queued this to merge now.