Fix SQLite3 support by checking the Ecto adapter name

To be specific, it fixes the :index and :show actions that were broken with the following error:

[error] GenServer #PID<0.1375.0> terminating
** (Ecto.QueryError) DISTINCT with multiple columns is not supported by SQLite3 in query:

from m0 in Ns.Chat.Message,
  as: :message,
  left_join: u1 in Ns.Accounts.User,
  as: :user,
  on: m0.user_id == u1.id,
  where: m0.id == ^...,
  distinct: [asc: m0.id],
  select: m0,
  preload: [:user]

    (ecto_sqlite3 0.16.0) lib/ecto/adapters/sqlite3/connection.ex:851: Ecto.Adapters.SQLite3.Connection.distinct/3
    (ecto_sqlite3 0.16.0) lib/ecto/adapters/sqlite3/connection.ex:859: Ecto.Adapters.SQLite3.Connection.select/2
    (ecto_sqlite3 0.16.0) lib/ecto/adapters/sqlite3/connection.ex:178: Ecto.Adapters.SQLite3.Connection.all/2
    (ecto_sqlite3 0.16.0) lib/ecto/adapters/sqlite3.ex:187: Ecto.Adapters.SQLite3.prepare/2
    (ecto 3.11.2) lib/ecto/query/planner.ex:182: Ecto.Query.Planner.query_without_cache/4
    (ecto 3.11.2) lib/ecto/query/planner.ex:152: Ecto.Query.Planner.query_prepare/6
    (ecto 3.11.2) lib/ecto/query/planner.ex:127: Ecto.Query.Planner.query_with_cache/8
    (ecto 3.11.2) lib/ecto/repo/queryable.ex:214: Ecto.Repo.Queryable.execute/4
    (ecto 3.11.2) lib/ecto/repo/queryable.ex:19: Ecto.Repo.Queryable.all/3
    (ecto 3.11.2) lib/ecto/repo/queryable.ex:162: Ecto.Repo.Queryable.one!/3
    (ns 0.1.0) lib/ns_web/live/admin/message_live.ex:5: NsWeb.Live.Admin.MessageLive.apply_action/2
    (ns 0.1.0) lib/ns_web/live/admin/message_live.ex:5: NsWeb.Live.Admin.MessageLive.handle_params/3
    (phoenix_live_view 1.0.0-rc.6) lib/phoenix_live_view/utils.ex:451: anonymous fn/5 in Phoenix.LiveView.Utils.call_handle_params!/5
    (telemetry 1.2.1) /home/igor/Code/nerdystreamer/deps/telemetry/src/telemetry.erl:321: :telemetry.span/3
    (phoenix_live_view 1.0.0-rc.6) lib/phoenix_live_view/channel.ex:909: Phoenix.LiveView.Channel.sync_handle_params_with_live_redirect/5
    (stdlib 6.0) gen_server.erl:2173: :gen_server.try_handle_info/3
    (stdlib 6.0) gen_server.erl:2261: :gen_server.handle_msg/6
    (stdlib 6.0) proc_lib.erl:329: :proc_lib.init_p_do_apply/3

Notes

Calls to_string to not depend on the module in the project, this is why I need to use the fully qualified name as well.
I'm unsure if MySQL needs similar handling.
Actually, I'm not sure if this is the most elegant way to handle this either.
Since this is the only distinct in the project does this fix all SQLite3 issues?

naymspace / backpex

Fix SQLite3 support by checking the Ecto adapter name #443

Notes