Merge pull request #160 from brownoxford/bugfix/159

fix: specify content-type headers when making json post requests

Author: Josh Holtz

lib/fastlane/plugin/firebase_app_distribution/client/firebase_app_distribution_api_client.rb

@@ -40,6 +40,7 @@ def enable_access(app_id, release_id, emails, group_ids)
         begin
           connection.post(enable_access_url(app_id, release_id), payload.to_json) do |request|
             request.headers["Authorization"] = "Bearer " + @auth_token
+            request.headers["Content-Type"] = "application/json"
           end
         rescue Faraday::ResourceNotFound
           UI.user_error!("#{ErrorMessage::INVALID_APP_ID}: #{app_id}")
@@ -67,6 +68,7 @@ def post_notes(app_id, release_id, release_notes)
         begin
           connection.post(release_notes_create_url(app_id, release_id), payload.to_json) do |request|
             request.headers["Authorization"] = "Bearer " + @auth_token
+            request.headers["Content-Type"] = "application/json"
           end
         rescue Faraday::ResourceNotFound
           UI.user_error!("#{ErrorMessage::INVALID_APP_ID}: #{app_id}")