[Elixir] Adding :package and :description to mix.exs template (#9945)

* feat: templating elixir's mix.exs :package and :description

* adding updated elixir sample

modules/openapi-generator/src/main/resources/elixir/mix.exs.mustache

@@ -7,6 +7,8 @@ defmodule {{moduleName}}.Mixfile do
      elixir: "~> {{supportedElixirVersion}}",
      build_embedded: Mix.env == :prod,
      start_permanent: Mix.env == :prod,
+     package: package(),
+     description: "{{appDescription}}",
      deps: deps()]
   end
 
@@ -34,4 +36,12 @@ defmodule {{moduleName}}.Mixfile do
 {{/deps}}
     ]
   end
+
+   defp package() do
+    [
+      name: "{{#underscored}}{{packageName}}{{/underscored}}",
+      files: ~w(lib mix.exs README* LICENSE*),
+      licenses: ["{{licenseId}}"]
+    ]
+  end
 end

samples/client/petstore/elixir/mix.exs

@@ -7,6 +7,8 @@ defmodule OpenapiPetstore.Mixfile do
      elixir: "~> 1.6",
      build_embedded: Mix.env == :prod,
      start_permanent: Mix.env == :prod,
+     package: package(),
+     description: "This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\",
      deps: deps()]
   end
 
@@ -33,4 +35,12 @@ defmodule OpenapiPetstore.Mixfile do
       {:poison, "~> 3.0"}
     ]
   end
+
+   defp package() do
+    [
+      name: "openapi_petstore",
+      files: ~w(lib mix.exs README* LICENSE*),
+      licenses: [""]
+    ]
+  end
 end