Better organisation of certificate files

[tkharju]

Currently LDAP certificate files are expected to be found from the project root: https://github.com/haltu/eca-auth-data/blob/db14f4b2acbe09068c5262311e35cd99dddf487c/authdata/external_sources.py#L254

These files are set in place with salt and never committed to this repository. It would be better to save these files outside the project directory. This will require changes to this repository and to the salt configuration.

DoD: Organize certificate files better. They should be outside of project root.