BUG - Duplicates are possible for Experiment.slug

[Evert-R]

While working on the experiment's duplicate function I noticed that the slug field on Experiment has not been set to Unique, so it's now possible to save multiple experiments with the same slug, which will not run, because only one experiment is expected.

I tried to migrate it the same way it is in Block:

slug = models.SlugField(max_length=64, unique=True, validators=[experiment_slug_validator])

but I got this error:

Applying experiment.0059_alter_experiment_slug...Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/utils.py", line 87, in _execute
    return self.cursor.execute(sql)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/psycopg/cursor.py", line 732, in execute
    raise ex.with_traceback(None)
psycopg.errors.DuplicateTable: relation "experiment_experiment_slug_63cd0f17_like" already exists

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/server/manage.py", line 24, in <module>
    main()
  File "/server/manage.py", line 20, in main
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.11/site-packages/django/core/management/__init__.py", line 442, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.11/site-packages/django/core/management/__init__.py", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.11/site-packages/django/core/management/base.py", line 412, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.11/site-packages/django/core/management/base.py", line 458, in execute
    output = self.handle(*args, **options)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/core/management/base.py", line 106, in wrapper
    res = handle_func(*args, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/core/management/commands/migrate.py", line 356, in handle
    post_migrate_state = executor.migrate(
                         ^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/migrations/executor.py", line 135, in migrate
    state = self._migrate_all_forwards(
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/migrations/executor.py", line 167, in _migrate_all_forwards
    state = self.apply_migration(
            ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/migrations/executor.py", line 252, in apply_migration
    state = migration.apply(state, schema_editor)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/migrations/migration.py", line 132, in apply
    operation.database_forwards(
  File "/usr/local/lib/python3.11/site-packages/django/db/migrations/operations/fields.py", line 235, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/base/schema.py", line 831, in alter_field
    self._alter_field(
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/postgresql/schema.py", line 304, in _alter_field
    self.execute(like_index_statement)
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/postgresql/schema.py", line 48, in execute
    return super().execute(sql, None)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/base/schema.py", line 201, in execute
    cursor.execute(sql, params)
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/utils.py", line 102, in execute
    return super().execute(sql, params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/utils.py", line 84, in _execute
    with self.db.wrap_database_errors:
  File "/usr/local/lib/python3.11/site-packages/django/db/utils.py", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/local/lib/python3.11/site-packages/django/db/backends/utils.py", line 87, in _execute
    return self.cursor.execute(sql)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/psycopg/cursor.py", line 732, in execute
    raise ex.with_traceback(None)
django.db.utils.ProgrammingError: relation "experiment_experiment_slug_63cd0f17_like" already exists