[AIRFLOW-XXX] Add doc on specifying SSH Key in SSH connection (apache…

…#5872)

docs/howto/connection/ssh.rst

@@ -40,6 +40,7 @@ Extra (optional)
     connection. The following parameters out of the standard python parameters
     are supported:
 
+    * **key_file** - Full Path of the private SSH Key file that will be used to connect to the remote_host.
     * **timeout** - An optional timeout (in seconds) for the TCP connect. Default is ``10``.
     * **compress** - ``true`` to ask the remote client/server to compress traffic; `false` to refuse compression. Default is ``true``.
     * **no_host_key_check** - Set to ``false`` to restrict connecting to hosts with no entries in ``~/.ssh/known_hosts`` (Hosts file). This provides maximum protection against trojan horse attacks, but can be troublesome when the ``/etc/ssh/ssh_known_hosts`` file is poorly maintained or connections to new hosts are frequently made. This option forces the user to manually add all new hosts. Default is ``true``, ssh will automatically add new host keys to the user known hosts files.
@@ -50,6 +51,7 @@ Extra (optional)
     .. code-block:: json
 
        {
+          "key_file": "/home/airflow/.ssh/id_rsa",
           "timeout": "10",
           "compress": "false",
           "no_host_key_check": "false",
@@ -64,4 +66,4 @@ Extra (optional)
 
     .. code-block:: bash
 
-        ssh://user:pass@localhost:22?timeout=10&compress=false&no_host_key_check=false&allow_host_key_change=true
+        ssh://user:pass@localhost:22?timeout=10&compress=false&no_host_key_check=false&allow_host_key_change=true&key_file=%2Fhome%2Fairflow%2F.ssh%2Fid_rsa