Functional Test for SnippetsFilter

[mpstefan]

As a maintainer of NGF
I want a functional test to cover the SnippetsFilter
So that I can verify that NGF is correctly interpreting the SnippetsFilter into NGINX configuration.

Acceptance

• The functional test should verify that:
  • The configuration specified in the SnippetsFilter is applied to the correct place in the NGINX configuration.
  • ...

[mpstefan]

Not technically blocked, but we want to do #2014 first.