Add completion route to client and add stop parameter where it's missing

[thomas-schillaci]

What does this PR do?

• Add the stop parameter to the completion route
• Add the completion method to the python client
• Add the stop parameter to the python client's chat method

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@Narsil

[drbh]

Hi @thomas-schillaci thank you for the contribution! This looks great but has a couple linting issues, these can be resolved by running the following command.

pre-commit run --all-files

PS: it looks like the CI passes once those are resolved: #1931

[thomas-schillaci]

@drbh thank you for the review, I've fixed the linting issues

[drbh]

LGTM. Thank you!!!

note: changes are exactly the same as #1931 and tests pass, so going to merge