--- a/libervia/backend/models/core.py	Fri Sep 06 17:38:31 2024 +0200
+++ b/libervia/backend/models/core.py	Fri Sep 06 17:40:32 2024 +0200
@@ -44,3 +44,14 @@
     message: dict[str, str]
     subject: dict[str, str] = Field(default_factory=dict)
     extra: dict[str, str] = Field(default_factory=dict)
+
+
+class DiscoIdentity(BaseModel):
+    """A single disco identity
+
+    Note that an XMPP entity may have several disco identities.
+    """
+
+    name: str
+    category: str
+    type: str

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/backend/models/types.py	Fri Sep 06 17:40:32 2024 +0200
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+
+# Libervia models custom types
+# Copyright (C) 2009-2024 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from typing import TYPE_CHECKING, Annotated, Any, TypeAlias, cast
+
+from pydantic import GetCoreSchemaHandler, GetJsonSchemaHandler
+from pydantic.json_schema import JsonSchemaValue
+from pydantic_core import core_schema
+from twisted.words.protocols.jabber.jid import JID
+
+
+class _JIDType:
+    """Use Twisted's JID in Python type, and serialize it to str
+
+    In Python, both JID and str are accepted, str are converted to JID.
+    """
+
+    @staticmethod
+    def validate_jid(value: str) -> JID:
+        return JID(value)
+
+    @staticmethod
+    def serialize_jid(jid: JID) -> str:
+        return str(jid)
+
+    @classmethod
+    def __get_pydantic_core_schema__(
+        cls, source_type: Any, handler: GetCoreSchemaHandler
+    ) -> core_schema.CoreSchema:
+        return core_schema.json_or_python_schema(
+            json_schema=core_schema.no_info_after_validator_function(
+                cls.validate_jid, core_schema.str_schema()
+            ),
+            python_schema=core_schema.union_schema(
+                [
+                    core_schema.is_instance_schema(JID),
+                    core_schema.no_info_after_validator_function(
+                        cls.validate_jid, core_schema.str_schema()
+                    ),
+                ]
+            ),
+            serialization=core_schema.plain_serializer_function_ser_schema(
+                cls.serialize_jid, when_used="json"
+            ),
+        )
+
+    @classmethod
+    def __get_pydantic_json_schema__(
+        cls, schema: core_schema.CoreSchema, handler: GetJsonSchemaHandler
+    ) -> JsonSchemaValue:
+        json_schema = handler(schema)
+        json_schema.update(
+            {
+                "format": "jid",
+                "description": "A valid Jabber ID (JID) in the format "
+                '"user@domain/resource"',
+            }
+        )
+        return json_schema
+
+
+class _StrictJIDType(_JIDType):
+    """Strict version of JIDType which only accept JID in Python."""
+
+    @classmethod
+    def __get_pydantic_core_schema__(
+        cls, source_type: Any, handler: GetCoreSchemaHandler
+    ) -> core_schema.CoreSchema:
+        return core_schema.json_or_python_schema(
+            json_schema=core_schema.no_info_after_validator_function(
+                cls.validate_jid, core_schema.str_schema()
+            ),
+            python_schema=core_schema.is_instance_schema(JID),
+            serialization=core_schema.plain_serializer_function_ser_schema(
+                cls.serialize_jid, when_used="json"
+            ),
+        )
+
+
+# We annotate the types so static type checker understand them as JID.
+JIDType = Annotated[JID, _JIDType]
+StrictJIDType = Annotated[JID, _StrictJIDType]