feat: Add support for client certs

[jadyndev]

This adds an option to use mtls when connecting to the firefly instance.
It relies on features from this PR: JC5/api-support-classes#6

[bnw]

Hi @jadyndev,
thanks für this PR.
I'm wondering: should the composer.lock be updated? Otherwise, if I checkout the repo and run composer install, won't it install the old version of api-support-classes that is missing the new cert feature?

[jadyndev]

Hi,
yes composer.lock should be updated.
I was unsure whether to do it in this PR or if you'd do this in the target branch.

[bnw]

Please include everything needed in the PR. After merge, the docker image will be immediately updated, using the master branch as is.

When you update the api-support-classes, please update as few other libraries as possible, to avoid errors.

When updating the api-support-classes version, did you have a look if there are other changes incoming, that could break something in the importer?

Thanks for you work! :)

[jadyndev]

I've updated composer.lock

  - Syncing firefly-iii/api-support-classes (dev-main a588e63) into cache
  - Upgrading voku/portable-ascii (1.6.1 => 2.0.3): Extracting archive
  - Installing symfony/polyfill-php83 (v1.31.0): Extracting archive
  - Installing psr/clock (1.0.0): Extracting archive
  - Installing symfony/clock (v7.2.0): Extracting archive
  - Installing carbonphp/carbon-doctrine-types (3.2.0): Extracting archive
  - Upgrading nesbot/carbon (2.57.0 => 3.8.4): Extracting archive
  - Upgrading illuminate/macroable (v8.83.8 => v11.38.2): Extracting archive
  - Upgrading illuminate/contracts (v8.83.8 => v11.38.2): Extracting archive
  - Installing illuminate/conditionable (v11.38.2): Extracting archive
  - Upgrading illuminate/collections (v8.83.8 => v11.38.2): Extracting archive
  - Upgrading illuminate/support (v8.83.8 => v11.38.2): Extracting archive
  - Upgrading firefly-iii/api-support-classes (dev-main a81ec1d => dev-main a588e63): Checking out a588e63afb from cache

The changes to firefly-iii/api-support-classes don't seem to break things and I haven't found any changes that would make me consider otherwise.
I have tested against Firefly III v6.1.10