ENH: Add datatypes and value classes to Extern C interface

Summary

See https://gitlab.indiscale.com/caosdb/customers/lfpb/management/-/issues/420. Adapts the

Focus

The single get_value functions are now split up into get_<datatype>_value, get_value_list_length, and get_<datatype>_list_value_at functions. Also, importances, roles, and datatypes are now cast from string to enums and back for getting and setting. In the case of datatypes, two additional Booleans for is_reference and is_list.

In addition, the way memory si allocated in case of char pointers has been fixed.

Test Environment

Unit tests and integration tests should be sufficient. Integration testing with deploy in f-grpc and server in f-grpc-f-consolidation, as usual.

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 specifications? Are they satisfied?

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

doc/CMakeLists.txt

@@ -81,10 +81,20 @@ if (DOXYGEN_FOUND)
                 -c ${CMAKE_CURRENT_BINARY_DIR}
                 ${CMAKE_CURRENT_BINARY_DIR}
                 sphinx_out
-            DEPENDS doc-doxygen
+                DEPENDS doc-doxygen
+                Examples.rst
+                README_SETUP.md
             WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
             COMMENT "Generating API documentation with Sphinx"
-            VERBATIM )
+            VERBATIM
+            )
+        # Copying files is necessary: https://stackoverflow.com/a/45808534/232888
+		# TODO fix for docs
+		#FILE(COPY
+		#Examples.rst
+		#README_SETUP.md
+            # Tutorial.rst
+			#DESTINATION "${CMAKE_CURRENT_BINARY_DIR}")
     else ()
         message("Sphinx need to be installed to generate the sphinx documentation")
     endif ()