ENH: Support FIND and COUNT queries

Summary

See https://gitlab.indiscale.com/caosdb/customers/lfpb/management/-/issues/399. Introduces FIND and Count queries.

Focus

Most changes are in transaction.h and transaction.cpp.

Test Environment

Unit and integration tests with server in f-grpc-f-query

Check List for the Author

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• 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/transaction.h

@@ -389,6 +389,23 @@ public:
     return this->request->requests_size();
   }
 
+  /**
+   * Get a JSON representation of the respone.
+   *
+   * For debugging.
+   */
+  inline auto ResponseToString() const -> const std::string {
+    google::protobuf::util::JsonOptions options;
+    std::string out;
+    google::protobuf::util::MessageToJsonString(*this->response, &out, options);
+    return out;
+  }
+
+  /**
+   * Get a JSON representation of the request.
+   *
+   * For debugging.
+   */
   inline auto RequestToString() const -> const std::string {
     google::protobuf::util::JsonOptions options;
     std::string out;