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

docs/sanic/request_data.md

@@ -204,9 +204,8 @@ The output will be:
 
 ## Accessing values using `get` and `getlist`
 
-The request properties which return a dictionary actually return a subclass of
-`dict` called `RequestParameters`. The key difference when using this object is
-the distinction between the `get` and `getlist` methods.
+The `request.args` returns a subclass of `dict` called `RequestParameters`. 
+The key difference when using this object is the distinction between the `get` and `getlist` methods.
 
 - `get(key, default=None)` operates as normal, except that when the value of
   the given key is a list, *only the first item is returned*.
@@ -223,6 +222,19 @@ args.get('titles') # => 'Post 1'
 args.getlist('titles') # => ['Post 1', 'Post 2']
 ```
 
+```python
+from sanic import Sanic
+from sanic.response import json
+
+app = Sanic(name="example")
+
+@app.route("/")
+def get_handler(request):
+    return json({
+        "p1": request.args.getlist("p1")
+    })
+```
+
 ## Accessing the handler name with the request.endpoint attribute
 
 The `request.endpoint` attribute holds the handler's name. For instance, the below