Add Gitlab pipeline buttons that regenerates messages and parsers
The buttons would be similar to the deploy buttons in stork.
I want this mainly for parsers because people regenerate with different bison versions. And Kea sometimes reaches a state where different bison versions are used for different parser files. And I don't know if it's safe to test Kea like that throughout the development process. And maybe people feel more comfortable clicking a button in Gitlab which adds a commit that regenerates the parsers for them with the bison version that was settled to be used than to keep upgrading the bison on their machine.
But we could add one for messages as well so that we don't have to --enable-generate-messages all the time.