As an admin, I cannot create a new theme

[coderberry]

Here is the error I get:

    * unique: themes_template_id_slug_index

If you would like to convert this constraint into an error, please
call unique_constraint/3 in your changeset and define the proper
constraint name. The changeset defined the following constraints:

    * unique: themes_slug_template_id_index

  File "lib/ecto/repo/schema.ex", line 574, in anonymous fn/4 in Ecto.Repo.Schema.constraints_to_errors/3
  File "lib/enum.ex", line 1314, in Enum."-map/2-lists^map/1-0-"/2
  File "lib/ecto/repo/schema.ex", line 559, in Ecto.Repo.Schema.constraints_to_errors/3
  File "lib/ecto/repo/schema.ex", line 222, in anonymous fn/14 in Ecto.Repo.Schema.do_insert/4
  File "lib/ecto/repo/schema.ex", line 774, in anonymous fn/3 in Ecto.Repo.Schema.wrap_in_transaction/6
...
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