The message service is used to transmit
information about a clicked repository
in the search information of the search page
to the search component.

Add metadata serach fields for programming language
and keywords of a repository.

Keyword search only works for some words
at the moment, might be an issue with elasticsearch.

Signed-off-by: Lukas Kaltenbrunner <lukas.kaltenbrunner@student.uibk.ac.at>