Motivation

Currently, if a user has TLS enabled and is using a custom CA that isn't
baked into the image, when the functions worker starts, it won't have
the CA in order to validate the cert presented by the broker.

Modifications

This adds support to have the KubernetesSecretsTokenAuthProvider
also distribute the CA via the same kubernetes secret used for the
token.

Verifying this change

• [x ] Make sure that the change passes the CI checks.

This change added tests and can be verified as follows:

• Added tests to ensure that the code paths work with and without a CA
• Added tests to ensure that the filename returned is as expected

Does this pull request potentially affect one of the following parts:

If yes was chosen, please highlight the changes

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no
• The rest endpoints: no
• The admin cli options: no
• Anything that affects deployment: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? not documented, but the KubernetesSecretsTokenAuthProvider is missing docs complete
• If a feature is not applicable for documentation, explain why? It does need docs, but the functionality as a whole is missing docs
• If a feature is not documented yet in this PR, please create a followup issue for adding the documentation