Add ssh-keys core plugin

plugins/ssh-keys/commands

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+[[ " help ssh-keys:help " == *" $1 "* ]] || exit "$DOKKU_NOT_IMPLEMENTED_EXIT"
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+case "$1" in
+  help | ssh-keys:help)
+    help_content_func () {
+      declare desc="return ssh-keys plugin help content"
+      cat<<help_content
+    ssh-keys, Manage public ssh keys that are allowed to connect to Dokku
+    ssh-keys:list, List of all authorized dokku public ssh keys
+    ssh-keys:add <name> [/path/to/key], Add a new public key by pipe or path
+    ssh-keys:remove <name>, Remove SSH public key by name
+help_content
+    }
+
+    if [[ $1 = "ssh-keys:help" ]] ; then
+        echo -e 'Usage: dokku ssh-keys[:COMMAND]'
+        echo ''
+        echo 'Manage public ssh keys that are allowed to connect to Dokku'
+        echo ''
+        echo 'Additional commands:'
+        help_content_func | sort | column -c2 -t -s,
+    else
+        help_content_func
+    fi
+    ;;
+
+  *)
+    exit "$DOKKU_NOT_IMPLEMENTED_EXIT"
+    ;;
+
+esac