doc: explain attachment functionality in help message & readme

README.md

@@ -16,10 +16,13 @@ it will try to query WKD,
 and if that fails keys.openpgp.org,
 for a public OpenPGP key belonging to the email address.
 
-Then it will send you a VCard file
+Then it will send you a VCard contact
 which contains the public key,
 so you can initiate an encrypted chat to it.
 
+You can also send a .asc PGP key file to the bot,
+and it will send you a VCard contact for it.
+
 With the "/generate-invite" command,
 you can also generate an invite link for the bot
 so you can publish it.

src/keyserver_bot/hooks.py

@@ -13,6 +13,9 @@ HELP_MSG = (
     "I will fetch it's public PGP key "
     "(from WKD and keys.openpgp.org) "
     "and send you a contact you can encrypt to."
+    "\n\n"
+    "If you send me a public PGP key, "
+    "you will also get a contact for it."
 )
 
 
@@ -51,7 +54,7 @@ def command(event):
     return snapshot.chat.send_file(vcard_path)
 
 
-def request_key_by_email(email) -> str:
+def request_key_by_email(email: str) -> str:
     domain = email.split("@")[1]
     public_key = request_from_wkd(email, domain)
     if not public_key:
@@ -62,7 +65,13 @@ def request_key_by_email(email) -> str:
 
 
 @hooks.on(events.RawEvent)
-def cleanup(event):
+def catch_events(event):
+    """This is called on every raw event and can be used for any kind of event handling.
+    Unfortunately deltachat-rpc-client doesn't offer high-level events for MSG_DELIVERED or SECUREJOIN_INVITER_PROGRESS
+    yet, so this needs to be done with raw events.
+
+    :param event: the event object
+    """
     print(event)
     if event.kind == EventType.MSG_DELIVERED or event.kind == EventType.MSG_FAILED:
         msg = Message(event.account, event.msg_id).get_snapshot()
@@ -74,7 +83,11 @@ def cleanup(event):
             chat.send_text(HELP_MSG)
 
 
-def delete_data(msg):
+def delete_data(msg: Message):
+    """For a message, delete the chat and all contacts which were in it to clean up.
+
+    :param msg: a Delta Chat Message snapshot
+    """
     contacts = msg.chat.get_contacts()
     msg.chat.delete()
     for member in contacts:
@@ -82,6 +95,7 @@ def delete_data(msg):
 
 
 def main():
+    """This is the CLI entry point."""
     run_bot_cli(hooks)