fix: configuring the start_link opts without global config

[yordis]

I tried the following:

defmodule Umbrella.Application do
  use Application

  @impl true
  def start(_type, _args) do
    children = [
      {Umbrella.EventStore.Client, connection_string: "esdb://localhost:2113?tls=true&tlsVerifyCert=false"}
    ]

    Supervisor.start_link(children, strategy: :one_for_one, name: Umbrella.Supervisor)
  end
end

WITHOUT configuring anything under config/* configuration files, thus, it failed because:

** (Mix) Could not start application umbrella: Umbrella.Application.start(:normal, []) returned an error: shutdown: failed to start child: Umbrella.EventStore.Client
    ** (EXIT) an exception was raised:
        ** (FunctionClauseError) no function clause matching in Keyword.merge/2
            (elixir 1.14.5) lib/keyword.ex:979: Keyword.merge(nil, [connection_string: "esdb://localhost:2113?tls=true&tlsVerifyCert=false"])
            (umbrella 0.1.0) lib/umbrella/event_store/client.ex:2: Umbrella.EventStore.Client.start_link/1
            (stdlib 5.0) supervisor.erl:420: :supervisor.do_start_child_i/3
            (stdlib 5.0) supervisor.erl:406: :supervisor.do_start_child/2
            (stdlib 5.0) supervisor.erl:390: anonymous fn/3 in :supervisor.start_children/2
            (stdlib 5.0) supervisor.erl:1256: :supervisor.children_map/4
            (stdlib 5.0) supervisor.erl:350: :supervisor.init_children/2
            (stdlib 5.0) gen_server.erl:962: :gen_server.init_it/2

[yordis]

Either this or force the config using fetch_env! (which I wouldn't recommend honestly)

[yordis]

@the-mikedavis do you mind giving me some love over here?

[coveralls]

Pull Request Test Coverage Report for Build a3e2bd96b6156044f5f028f296fd76e069669bf2-PR-88

Warning: This coverage report may be inaccurate.

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• 0 of 0 changed or added relevant lines in 0 files are covered.
• 356 unchanged lines in 25 files lost coverage.
• Overall coverage decreased (-50.2%) to 49.365%

---

Files with Coverage Reduction	New Missed Lines	%
lib/spear/acl.ex	1	90.0%
lib/spear/connection/configuration.ex	1	96.77%
lib/spear/filter/checkpoint.ex	1	0.0%
lib/spear/grpc.ex	1	83.33%
lib/spear/position.ex	1	0.0%
lib/spear/scavenge.ex	1	0.0%
lib/spear/supported_rpc.ex	1	0.0%
lib/spear/uuid.ex	1	90.0%
lib/spear/filter.ex	2	93.33%
lib/spear/cluster_member.ex	3	0.0%
<!--	Total:	356		-->

Totals
Change from base Build 40d5f2f12eae2090e90d0d5e5cddf50329ff1222:	-50.2%
Covered Lines:	350
Relevant Lines:	709

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💛 - Coveralls