Add support for LDAP user authentication

[rx294]

Add support for for LDAP and LDAPS authentication for heimdall2.

In the initial iteration, the setup could be done over API calls. The API way has the benefit of avoiding plain-text files with LDAP password.

It also allows for setup through env vars for docker/k8s deployments.
For traditional deployments we could develop a script + yaml conf file to automate the setup.

We could make localhost based actions non-authenticated allowing for automated setups.

Later the API could be hooked View panels to allow UI based setup.

Example on how gitlab deployment allows for LDAP setup through env vars

https://github.com/sameersbn/docker-gitlab/blob/e95c3b744af2ed0302424c40c049717630522b67/README.md#available-configuration-parameters