add: implement language switch for contract and update contract text The texts for the contracts are taken from https://git.ccs-baumann.de/wpia/policies/tree/master/ra_agent_contract and are maintained there. Change-Id: I384176bb8d833f0dc74d438c461bf8114bf5a12c
add: handling of RA Agent Contract Only covers the basic functionality. The full text of the contract and the email will be covered in a later patch. The data contract.id and contract.token will be used for pdf-output in a later patch. The implementation of the restrictions connected to signed contract will be covered in a later patch. Change-Id: I5b47d31458779d227a4f9702a9e7563ab210e7e5