Add .clear_messages() method to django.contrib.messages

[benjaoming]

Disclaimer: This is really a minor issue 😊

We can do:

from django.contrib.messages import get_messages

And then we can call get_messages() - and if we iterate over them, they will be cleared.

But we can't explicitly clear them because this method doesn't exist:

from django.contrib.messages import clear_messages

For me, the use-case was test-related: Writing an e2e test case that calls some views and at each step verified messages, then cleared them.

Not sure if adding the method would make people use the messages framework wrongly, but I think it makes sense to note that ADDING clear_messages to the mix might make some people think you need to call it... which in most cases, you don't, and therefore the documentation needs to be clear (pun intended).

Forum discussion: ​https://forum.djangoproject.com/t/why-isnt-it-easier-to-clear-messages/5727/7

[Sarah Boyce]

Accepting without requesting this be added to the new features board as this is based off an existing older discussion with already a good consensus that this is useful and a small addition

[Natalia Bidart]

My only request would be to name this consistently with how we reset the queries:

>>> from django.db import connection, reset_queries
>>> connection.queries
[]
>>> reset_queries()
>>>

Therefore I think the function should be called reset_messages().