UserIdentity: Too long index names

[rhblind]

After this commit on AshPostgres, indices generated on user identities may easily be too long.

Identity module

defmodule MyApp.Domain.Account.UserIdentity do
  use Ash.Resource,
    domain: MyApp.Domain.Account,
    data_layer: AshPostgres.DataLayer,
    extensions: [AshAuthentication.UserIdentity]

  user_identity do
    domain MyApp.Domain.Account
    user_resource MyApp.Domain.Account.User
  end

  postgres do
    repo MyApp.AshRepo
    table "account_user_identity"
  end
end

Traceback

** (EXIT from #PID<0.98.0>) an exception was raised:
    ** (Spark.Error.DslError) [MyApp.Domain.Account.UserIdentity]
postgres -> identity_index_names -> account_user_identity_unique_on_strategy_and_uid_and_user_id_index:
  Identity unique_on_strategy_and_uid_and_user_id has a name that is too long. Names must be 63 characters or less.

Please configure an index name for this identity in the `identity_index_names` configuration. For example:application

postgres do
  identity_index_names :unique_on_strategy_and_uid_and_user_id: "a_shorter_name"
end

        (ash_postgres 2.0.12) lib/verifiers/validate_identity_index_names.ex:43: anonymous fn/2 in AshPostgres.Verifiers.ValidateIdentityIndexNames.verify/1
        (elixir 1.16.3) lib/enum.ex:992: anonymous fn/3 in Enum.each/2
        (stdlib 5.2) maps.erl:416: :maps.fold_1/4
        (elixir 1.16.3) lib/enum.ex:2540: Enum.each/2
        (ash_postgres 2.0.12) lib/verifiers/validate_identity_index_names.ex:30: AshPostgres.Verifiers.ValidateIdentityIndexNames.verify/1
        lib/myapp/domain/account/resources/identity.ex:1: anonymous fn/1 in 
MyApp.Domain.Account.UserIdentity.__verify_spark_dsl__/1
        (elixir 1.16.3) lib/enum.ex:987: Enum."-each/2-lists^foreach/1-0-"/2
        lib/myapp/domain/account/resources/identity.ex:1: MyApp.Domain.Account.UserIdentity.__verify_spark_dsl__/1

The generated index account_user_identity_unique_on_strategy_and_uid_and_user_id_index is 66 characters long, while the changes introduced in AshPostgres limits indices to maximum 63 characters.