Remove deaddrop chat

Contact request chats are not merged into a single virtual "deaddrop"
chat anymore. Instead, they are shown in the chatlist the same way as
other chats, but sending of messages to them is not allowed and MDNs
are not sent automatically until the chat is "accepted" by the user.

New API:
- dc_chat_is_contact_request(): returns true if chat is a contact
request.  In this case option to accept and block the chat via
dc_accept_chat() and dc_block_chat() should be shown in the UI.
- dc_accept_chat(): accept contact request and unblock the chat
- dc_block_chat(): decline contact request and block the chat

Removed API:
- dc_create_chat_by_msg_id(): deprecated 2021-02-07 in favor of
  dc_decide_on_contact_request()
- dc_marknoticed_contact(): deprecated 2021-02-07 in favor of
  dc_decide_on_contact_request()
- dc_decide_on_contact_request(): this call requires a message ID from
  deaddrop chat as input. As deaddrop chat is removed, this call can't
  be used anymore.
- dc_msg_get_real_chat_id(): use dc_msg_get_chat_id() instead, the
  only difference between these calls was in handling of deaddrop chat
- removed DC_CHAT_ID_DEADDROP and DC_STR_DEADDROP constants

python/tests/test_account.py

@@ -909,12 +909,11 @@ class TestOnlineAccount:
         msg_in = ac2.get_message_by_id(msg_out.id)
         assert msg_in.text == "message2"
 
-        lp.sec("ac2: check that the message arrive in deaddrop")
+        lp.sec("ac2: check that the message arrived in a chat")
         chat2 = msg_in.chat
         assert msg_in in chat2.get_messages()
         assert not msg_in.is_forwarded()
-        assert chat2.is_deaddrop()
-        assert chat2 == ac2.get_deaddrop_chat()
+        assert chat2.is_contact_request()
 
         lp.sec("ac2: create new chat and forward message to it")
         chat3 = ac2.create_group_chat("newgroup")
@@ -979,16 +978,16 @@ class TestOnlineAccount:
         assert not msg2.is_forwarded()
         assert msg2.get_sender_contact().display_name == ac1.get_config("displayname")
 
-        lp.sec("check the message arrived in contact-requests/deaddrop")
+        lp.sec("check the message arrived in contact request chat")
         chat2 = msg2.chat
         assert msg2 in chat2.get_messages()
-        assert chat2.is_deaddrop()
+        assert chat2.is_contact_request()
         assert chat2.count_fresh_messages() == 1
         assert msg2.time_received >= msg1.time_sent
 
         lp.sec("create new chat with contact and verify it's proper")
         chat2b = msg2.create_chat()
-        assert not chat2b.is_deaddrop()
+        assert not chat2b.is_contact_request()
         assert chat2b.count_fresh_messages() == 1
 
         lp.sec("mark chat as noticed")
@@ -1853,7 +1852,7 @@ class TestOnlineAccount:
 
         lp.sec("ac2: wait for receiving message and avatar from ac1")
         msg2 = ac2._evtracker.wait_next_messages_changed()
-        assert msg2.chat.is_deaddrop()
+        assert msg2.chat.is_contact_request()
         received_path = msg2.get_sender_contact().get_profile_image()
         assert open(received_path, "rb").read() == open(p, "rb").read()
 
@@ -1928,6 +1927,8 @@ class TestOnlineAccount:
         ev = in_list.get(timeout=10)
         assert ev.action == "chat-modified"
         ev = in_list.get(timeout=10)
+        assert ev.action == "chat-modified"
+        ev = in_list.get(timeout=10)
         assert ev.action == "added"
         assert ev.message.get_sender_contact().addr == ac1_addr
         assert ev.contact.addr == "devnull@testrun.org"