DOC: Add sections to documentation

Summary

See https://gitlab.indiscale.com/caosdb/customers/lfpb/management/-/issues/409. Add sections, placeholders for examples, and automatically generated docs to the documentation.

Focus

Verify that the structure makes sense.

Test Environment

Build the documentation as described in README_SETUP.md

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related Issues
• [ ] Up-to-date CHANGELOG.md
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• [ ] Up-to-date CHANGELOG.md
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there spezifications? Are they satisfied?

For further good practices have a look at our review guidelines.

docs/src/index.md

@@ -10,10 +10,18 @@ CaosDB.Utility.get_env_var(::AbstractString, ::AbstractString)
 ```
 
 
-## Semi-auomatic generation of documentation
+## Public API
 
 Similar to autodoc:
 
 ```@autodocs
-Modules=[CaosDB]
+Modules=[CaosDB, CaosDB.Info, CaosDB.Utility, CaosDB.Connection, CaosDB.Authentication, CaosDB.Entity]
+Private=false
+```
+
+## Expert-use only API functions
+
+```@autodocs
+Modules=[CaosDB, CaosDB.Info, CaosDB.Utility, CaosDB.Connection, CaosDB.Authentication, CaosDB.Entity]
+Public=false
 ```