Compatibility with Elixir v1.15 (#115)

* Use static list instead of Logger.levels/0

Logger.levels/0 was just introduced in elixir v1.16

* Changes required elixir version to v1.15.1

* Adds elixir v1.15.1 to CI matrix

* Update mix.exs

---------

Co-authored-by: Andrew Dryga <andrew@dryga.com>

.github/workflows/ci.yml

@@ -24,6 +24,8 @@ jobs:
         include:
           - otp-version: 24.3
             elixir-version: 1.16
+          - otp-version: 25
+            elixir-version: 1.15.1
           - otp-version: 25
             elixir-version: 1.16
             check-formatted: true

lib/logger_json.ex

@@ -67,7 +67,7 @@ defmodule LoggerJSON do
     * `:conn` - the `Plug.Conn` struct. This is useful when logging HTTP requests and responses,
     each formatter may use it differently.
   """
-  @log_levels Logger.levels()
+  @log_levels [:error, :info, :debug, :emergency, :alert, :critical, :warning, :notice]
   @log_level_strings Enum.map(@log_levels, &to_string/1)
 
   @doc """

mix.exs

@@ -8,7 +8,7 @@ defmodule LoggerJSON.Mixfile do
     [
       app: :logger_json,
       version: @version,
-      elixir: "~> 1.16",
+      elixir: "~> 1.16 or ~> 1.15.1",
       elixirc_paths: elixirc_paths(Mix.env()),
       compilers: [] ++ Mix.compilers(),
       build_embedded: Mix.env() == :prod,