matrix-corporal manages your Matrix server according to a configuration policy.

The point is to have a single source of truth about users/rooms somewhere
(say in an external system, like your intranet), and have something
(matrix-corporal) continually reconfigure your Matrix server in accordance with it.

In a way, it can be thought of as "Kubernetes for Matrix", in that it takes such
a JSON policy as an input, and performs reconciliation with the Matrix server --
creating, activating, disabling user accounts, making them (automatically)
join/leave rooms, etc.

Besides reconciliation, matrix-policy also does firewalling (acts as a gateway).
You can put matrix-corporal in front of your Matrix Synapse server, and have it
capture all Matrix API requests and allow/deny them in accordance with the policy.

With reconciliation and firewalling both working together, matrix-corporal
ensures that your Matrix server's state always matches what the policy says, and
that no user is allowed to perform actions which take the server out of that
equilibrium.