Document server code structure

Document the server code structure: Schedules, Jobs, Transactions, BackendTransactions and backend specific implementations.

---

Summary

This MR introduces documentation for the server's code structure.

Additionally, a lot of documentation files received smaller fixes, for example dead links were replaced.

Focus

• Is the documentation content correct?
• Can the documentation be understood by new developers?
• Are the documentation pages (html and images) produced correctly?

Test Environment

• make doc, then direct your browser to build/doc/html/development/structure.html
• Test artefact generates by the pipeline (deploy > pages_prepare).

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 behaviour is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?
• Removed f-doc-structure line from .gitlab-ci.yml before merging.

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

src/doc/development/structure.rst

@@ -30,8 +30,12 @@ Transactions are explained in detail in the :ref:`Transactions and Schedules<tra
 .. uml::
 
   @startuml
-  abstract AbstractCaosDBServerResource
-  class RetrieveEntityResource
+  abstract AbstractCaosDBServerResource {
+    {abstract} httpGetInChildClass()
+    {abstract} httpPostInChildClass()
+    {abstract} ...InChildClass()
+  }
+  abstract RetrieveEntityResource
   class EntityResource
   AbstractCaosDBServerResource <|-- RetrieveEntityResource
   RetrieveEntityResource <|-- EntityResource
@@ -60,6 +64,43 @@ main packages which handle the backend:
     method.  These classes may use specific backend implementations (like for example the MySQL
     implementations) to interact with the backend database.
 
+
+.. uml::
+
+  @startuml
+  together {
+    abstract BackendTransaction {
+      HashMap impl // stores all implementations
+      abstract execute()
+    }
+    note left of BackendTransaction::impl
+      Stores the
+      implementation
+      for each
+      interface."
+    end note
+    package ...backend.interfaces {
+      interface GetIDByNameImpl {
+        abstract execute(String name, String role, String limit)
+      }
+    }
+  }
+  together {
+    package ...backend.transaction {
+      class GetIDByName extends BackendTransaction {
+        execute()
+      }
+    }
+    package ...backend.implementation.MySQL {
+      class MySQLGetIDByName implements GetIDByNameImpl {
+        execute(String name, String role, String limit)
+      }
+    }
+  }
+
+  GetIDByName::execute --r-> MySQLGetIDByName
+  @enduml
+
 .. _transactions:
 
 Transactions and Schedules