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.

include/caosdb/data_type.h

@@ -151,6 +151,22 @@ public:
   DataType(const std::string &data_type) : DataType() {
     this->wrapped->mutable_reference_data_type()->set_name(data_type);
   }
+
+  inline static auto ListOf(const AtomicDataType &atomic_data_type)
+    -> DataType {
+    DataType result;
+    result.wrapped->mutable_list_data_type()->set_atomic_data_type(
+      static_cast<ProtoAtomicDataType>(atomic_data_type));
+    return result;
+  }
+  inline static auto ListOf(const std::string reference_data_type) -> DataType {
+    DataType result;
+    result.wrapped->mutable_list_data_type()
+      ->mutable_reference_data_type()
+      ->set_name(reference_data_type);
+    return result;
+  }
+
   [[nodiscard]] inline auto IsAtomic() const noexcept -> bool {
     return this->wrapped->data_type_case() == DataTypeCase::kAtomicDataType;
   }