Remove DoGuard from TCommand

1) Remove: DoGuard from TCommand
1) Add documentation: to check all mandatory injections with `Assert` calls at the very begging of the `DoExecute` method

Locate TCommand and its DoExecute method, then inspect how DoGuard and mandatory injections are used. Remove DoGuard, document the required Assert checks at the beginning of DoExecute, and verify that the resulting documentation matches the mandatory injections.

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