+ Modules gating using Greenwave

+ ==============================

+ 

+ Every successfully built module is moved to ``done`` state. Modules in this state cannot

+ be used as a build-dependency for other modules. They need to be moved to ``ready`` state.

+ 

+ By default, MBS moves the module from ``done`` state to ``ready`` state automatically,

+ but MBS can also be configured to gate move from ``done`` to ``ready`` state according

+ to Greenwave service.

+ 

+ When Greenwave integration is configured, then following additional MBS features are enabled:

+ 

+ - When the module is moved to ``done`` state, Greenwave is queried to find out whether to module

+   can be moved to ``ready`` state instantly.

+ - If the module cannot be moved to ``ready`` state yet, MBS keeps the module build in the

+   ``done`` state and waits for a message from Greenwave. If this message says that all the

+   tests defined by Greenwave policy have passed, then the module build is moved to ``ready``

+   state.

+ - MBS also queries Greenwave periodically to find out the current gating status for modules

+   in the ``done`` state. This is useful in case when message from Greenwave has been lost.