Support disabled timescaledb

[Alexsaphir]

📣 Feedback / 🐛 Bugs

Trying to self host codecov, SETUP__TIMESERIES__ENABLED set to false.

The migrations failed, I suppose since there is no timeseries database set up.
If running codecov without timeseries enable is still supported, the migrations for this part should not be enabled in this case.

(Output from the api container, the code seem to correspond to this repo)

{"message": "Codecov is starting migrations...", "asctime": "2024-06-24 20:01:50,410", "name": "shared.django_apps.legacy_migrations.management.commands.migrate", "levelname": "INFO", "lineno": 116, "pathname": "/usr/local/lib/python3.12/site-packages/shared/django_apps/legacy_migrations/management/commands/migrate.py", "funcName": "handle", "threadName": "MainThread", "taskName": null, "logger.name": "shared.django_apps.legacy_migrations.management.commands.migrate", "logger.thread_name": "MainThread", "level": "INFO"}
Traceback (most recent call last):
  File "/usr/local/lib/python3.12/site-packages/django/utils/connection.py", line 58, in __getitem__
    return getattr(self._connections, alias)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/asgiref/local.py", line 105, in __getattr__
    raise AttributeError(f"{self!r} object has no attribute {key!r}")
AttributeError: <asgiref.local.Local object at 0x77f4ef154470> object has no attribute 'timeseries'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/app/manage.py", line 17, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.12/site-packages/django/core/management/__init__.py", line 442, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.12/site-packages/django/core/management/__init__.py", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.12/site-packages/django/core/management/base.py", line 412, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.12/site-packages/django/core/management/base.py", line 458, in execute
    output = self.handle(*args, **options)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/shared/django_apps/legacy_migrations/management/commands/migrate.py", line 118, in handle
    db_connection = connections[database]
                    ~~~~~~~~~~~^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/django/utils/connection.py", line 61, in __getitem__
    raise self.exception_class(f"The connection '{alias}' doesn't exist.")
django.utils.connection.ConnectionDoesNotExist: The connection 'timeseries' doesn't exist.