Add support for pre/post hooks

src/libexec/saturnin-iam

 }
 
 
+#
+# hooks
+#
+
+run_hook() {
+    local name=$1
+    local cmd=$2
+    local arg=$3
+    saturnin conf -p iam.hooking.$name.$cmd \
+      | SATURNIN_IAM_CMD=$cmd \
+        SATURNIN_IAM_ARG=$arg \
+        bash
+}
+
+
 #
 # subcommand handlers
 #
 
 shift
 
+run_hook before $cmd $1
 i_am_$cmd $1
+run_hook after $cmd $1