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.

src/ccaosdb.cpp

@@ -824,26 +824,6 @@ ERROR_RETURN_CODE(GENERIC_ERROR,
                     return 0;
                   })
 
-// TODO(fspreck) Fix this somehow. It segfaults. Bleh.
-// ERROR_RETURN_CODE(GENERIC_ERROR,
-//                   int caosdb_entity_property_get_string_list_value(
-//                     caosdb_entity_property *property, char ***out),
-//                   {
-//                     auto *wrapped_property = WRAPPED_PROPERTY_CAST(property);
-//                     auto value_list = wrapped_property->GetValue().AsList();
-//                     delete[] * out;
-//                     std::vector<char *> out_list;
-//                     char *tmp;
-//                     out_list.reserve(value_list.size());
-//                     for (size_t i = 0; i < value_list.size(); i++) {
-//                       tmp = new char[value_list[i].AsString().size() + 1];
-//                       strcpy(tmp, value_list[i].AsString().c_str());
-//                       out_list.push_back(tmp);
-//                     }
-//                     *out = &out_list[0];
-//                     return 0;
-//                   })
-
 ERROR_RETURN_CODE(GENERIC_ERROR,
                   int caosdb_entity_property_get_value_list_length(caosdb_entity_property *property,
                                                                    int *out),