feat(docs): add LDAP, Identity, Auth, Depl. Descr.

add docs on
- LDAP (User guide + installation guide)
- Identity Service
- Authorization Service
- Deployment Descriptor Reference

related to #CAM-819, #CAM-833, #CAM-978
Merge branch 'master' of github.com:camunda/docs.camunda.org

Conflicts:
	site/src/documents/guides/user-guide/chapters/01-bpm-platform.md.eco