api!(jsonrpc): chat_type now contains a variant of a string enum/union. Affected places: FullChat.chat_type, BasicChat.chat_type, ChatListItemFetchResult::ChatListItem.chat_type, Event:: SecurejoinInviterProgress.chat_type and MessageSearchResult.chat_type (#7285)

Actually it will be not as breaking if you used the constants, because
this pr also changes the constants.

closes #7029 

Note that I had to change the constants from enum to namespace, this has
the side effect, that you can no longer also use the constants as types,
you need to instead prefix them with `typeof ` now.

deltachat-rpc-client/src/deltachat_rpc_client/const.py

@@ -91,19 +91,17 @@ class ChatId(IntEnum):
     LAST_SPECIAL = 9
 
 
-class ChatType(IntEnum):
+class ChatType(str, Enum):
     """Chat type."""
 
-    UNDEFINED = 0
-
-    SINGLE = 100
+    SINGLE = "Single"
     """1:1 chat, i.e. a direct chat with a single contact"""
 
-    GROUP = 120
+    GROUP = "Group"
 
-    MAILINGLIST = 140
+    MAILINGLIST = "Mailinglist"
 
-    OUT_BROADCAST = 160
+    OUT_BROADCAST = "OutBroadcast"
     """Outgoing broadcast channel, called "Channel" in the UI.
 
     The user can send into this channel,
@@ -115,7 +113,7 @@ class ChatType(IntEnum):
     which would make it hard to grep for it.
     """
 
-    IN_BROADCAST = 165
+    IN_BROADCAST = "InBroadcast"
     """Incoming broadcast channel, called "Channel" in the UI.
 
     This channel is read-only,