nixos/ceph: Clarify comments in tests and add source reference for the bootstraping method

nixos/tests/ceph-multi-node.nix

@@ -104,6 +104,10 @@ let
     };
   }; };
 
+  # Following deployment is based on the manual deployment described here:
+  # https://docs.ceph.com/docs/master/install/manual-deployment/
+  # For other ways to deploy a ceph cluster, look at the documentation at
+  # https://docs.ceph.com/docs/master/
   testscript = { ... }: ''
     startAll;
 

nixos/tests/ceph-single-node.nix

@@ -69,6 +69,10 @@ let
     };
   }; };
 
+  # Following deployment is based on the manual deployment described here:
+  # https://docs.ceph.com/docs/master/install/manual-deployment/
+  # For other ways to deploy a ceph cluster, look at the documentation at
+  # https://docs.ceph.com/docs/master/
   testscript = { ... }: ''
     startAll;