Make displayname max length configurable

mautrix_telegram/config.py

@@ -79,6 +79,7 @@ class Config(BaseBridgeConfig):
         copy("bridge.displayname_template")
 
         copy("bridge.displayname_preference")
+        copy("bridge.displayname_max_length")
 
         copy("bridge.max_initial_member_sync")
         copy("bridge.sync_channel_members")

mautrix_telegram/puppet.py

@@ -256,7 +256,8 @@ class Puppet(CustomPuppetMixin):
             self.displayname = displayname
             self.displayname_source = source.tgid
             try:
-                await self.default_mxid_intent.set_displayname(displayname[:100])
+                await self.default_mxid_intent.set_displayname(
+                    displayname[:config["bridge.displayname_max_length"]])
             except MatrixRequestError:
                 self.log.exception("Failed to set displayname")
                 self.displayname = ""