Add Mastodon API service class, auth token config

Add a new REST API service class to keep things DRY

app/services/rest_api_service.rb

@@ -0,0 +1,27 @@
+class RestApiService < ApplicationService
+  private
+
+    def base_url
+      raise NotImplementedError
+    end
+
+    def headers
+      raise NotImplementedError
+    end
+
+    def endpoint_url(path)
+      "#{base_url}/#{path.gsub(/^\//, '')}"
+    end
+
+    def get(path, params = {})
+      res = Faraday.get endpoint_url(path), params, headers
+      # TODO handle unsuccessful responses with no valid JSON body
+      JSON.parse(res.body)
+    end
+
+    def post(path, payload)
+      res = Faraday.post endpoint_url(path), payload.to_json, headers
+      # TODO handle unsuccessful responses with no valid JSON body
+      JSON.parse(res.body)
+    end
+end