add x-add-key command, add example how to update your key

schleuder/docs/subscribers.md

@@ -8,13 +8,64 @@ title: Documentation for subscribers
 
 #### Subscription and key management
 
-The following keywords must be send to the request address of the list: `foo-request@hostname`.
+The following keywords must be send to the request address of the list: `foo-request@hostname`.  
+Include `x-list-name: foo@hostname` with every command you send.
 
+**x-add-key:**  
+Import the attachment(s) or the rest of the email-body into the list’s keyring. Only ascii-armored keys are supported.
+
+**x-set-fingerprint: 0x12345678DEADBEEF12345678DEADBEEF12345678**  
+Assign the key with the given fingerprint to your subscription. It is not possible to set an empty fingerprint. To unset your fingerprint use `x-unset-fingerprint`.
+
+**x-unset-fingerprint: person@example.org**  
+Remove the fingerprint associated with your subscription.
+
+#### Example: Updating you key for a list
+
+All commands to switch to a **new** key must be signed with the current **old** key. 
+
+**1. submit new key to lists keyring**
+
+```
+x-list-name: foo@hostname
+x-add-key
+
+-----BEGIN PGP PUBLIC KEY BLOCK-----
+
+ASak6ezpIZkSZ/ql7UOiOIxi7dAWg4YwFB+yrkN+aUi9Io+No1Y0Rjz+/pUIvGx7
+KbyhUQjE6wvGJKDqWyLQVoyB+R0ZV3k6lQFqa7TETXCoGuU8CRM4XcynU7MNgGFQ
+...
+mDMEXuYDuxYJKwYBBAHaRw8BAQdAqP98Ao=
+=32SG
+-----END PGP PUBLIC KEY BLOCK-----
+```
+
+A successful answer should look something like this:
+> This key was newly added:
+0x12345678DEADBEEF12345678DEADBEEF12345678 youraccount@yourmail.net 2019-05-23 [expires: 2023-05-23] 
+
+**2. verify that uploaded key made it into the keyring**
+
+```
+x-list-name: foo@hostname
+x-list-keys
+
+```
+The answer will list all keys in the lists keyring. Make sure, your **new** key is in the keyring now.
+
+**3. change you subscription to use the new key**
+
+```
+x-list-name: foo@hostname
 x-set-fingerprint: 0x12345678DEADBEEF12345678DEADBEEF12345678
-: Assign the key with the given fingerprint to your subscription. It is not possible to set an empty fingerprint. To unset your fingerprint use `x-unset-fingerprint`.
+```
+
+A successful answer should look something like this:
+> Fingerprint for youraccount@yourmail.net set to 12345678DEADBEEF12345678DEADBEEF12345678.
+
+From now on, all mails will be encrpyted to the **new** key
+and all your mails must be signed with this key.
 
-x-unset-fingerprint: person@example.org
-: Remove the fingerprint associated with your subscription.
 
 #### Resending