wilco_dtc_supportd daemon

Please see ../README.md for general information.

IPC mechanisms

This daemon uses three IPC mechanisms:

• gRPC - for talking to the wilco_dtc daemon.
• Mojo - for talking to the browser.
• D-Bus - for receiving Mojo bootstrap requests from the browser.

Class structure

`Daemon`
 ^
 |
 v
`Core`
 ^
 |
 |   // gRPC-related members:
 +-> `GrpcService`
 |       (handles incoming gRPC requests)
 +-> `AsyncGrpcServer<grpc_api::WilcoDtcSupportd>`
 |       (connects `GrpcService` with the actual gRPC
 |        pipe)
 +-> `AsyncGrpcClient<grpc_api::WilcoDtc>`
 |       (sends outgoing gRPC requests through the actual gRPC pipe)
 |
 |   // Mojo-related members:
 +-> `MojoService`
 |       (handles incoming Mojo requests and sends outgoing ones)
 +-> `mojo::Binding<mojom::WilcoDtcSupportdService>`
 |       (connects `MojoService` with the actual Mojo pipe)
 +-> `RoutineService`
 |       (handles diagnostics routines requests to cros_healthd)
 +-> `ProbeService`
 |       (handles probe requests to cros_healthd)
 |
 |   // D-Bus-related members:
 +-> `DBusService`
 |       (handles incoming D-Bus requests)
 +-> `brillo::dbus_utils::DBusObject`
         (connects `DBusService` with the actual D-Bus pipe)

Classes are generally organized such that they don't know about their owners or siblings in this graph. Instead, these classes are parameterized with delegate(s), which implement these cross-class calls. This allows to test each individual piece of logic separately.