fix SERVER_NAME enforcement in url_for and request.args documentation (#1708)

* 🐛 fix SERVER_NAME enforcement in url_for

fixes #1707

* 💡 add additional documentation for using request.args

fixes #1704

* ✅ add additional test to check url_for without SERVER_NAME

* 📝 add changelog for fixes

changelogs/1704.doc.rst

@@ -0,0 +1,3 @@
+Fix documentation for `get` and `getlist` of the `request.args`
+
+Add additional example for showing the usage of `getlist` and fix the documentation string for `request.args` behavior

changelogs/1707.bugfix.rst

@@ -0,0 +1,4 @@
+Fix `url_for` behavior with missing SERVER_NAME
+
+If the `SERVER_NAME` was missing in the `app.config` entity, the `url_for` on the `request` and  `app` were failing
+due to an `AttributeError`. This fix makes the availability of `SERVER_NAME` on our `app.config` an optional behavior.