Split admin API for reported events into a detail and a list view (#8539)

Split admin API for reported events in detail und list view.
API was introduced with #8217 in synapse v.1.21.0.

It makes the list (`GET /_synapse/admin/v1/event_reports`) less complex and provides a better overview.
The details can be queried with: `GET /_synapse/admin/v1/event_reports/<report_id>`.
It is similar to room and users API.

It is a kind of regression in `GET /_synapse/admin/v1/event_reports`.  `event_json` was removed. But the api was introduced one version before and it is an admin API (not under spec).

Signed-off-by: Dirk Klimpel dirk@klimpel.org

synapse/rest/admin/event_reports.py

@@ -15,7 +15,7 @@
 
 import logging
 
-from synapse.api.errors import Codes, SynapseError
+from synapse.api.errors import Codes, NotFoundError, SynapseError
 from synapse.http.servlet import RestServlet, parse_integer, parse_string
 from synapse.rest.admin._base import admin_patterns, assert_requester_is_admin
 
@@ -86,3 +86,47 @@ class EventReportsRestServlet(RestServlet):
             ret["next_token"] = start + len(event_reports)
 
         return 200, ret
+
+
+class EventReportDetailRestServlet(RestServlet):
+    """
+    Get a specific reported event that is known to the homeserver. Results are returned
+    in a dictionary containing report information.
+    The requester must have administrator access in Synapse.
+
+    GET /_synapse/admin/v1/event_reports/<report_id>
+    returns:
+        200 OK with details report if success otherwise an error.
+
+    Args:
+        The parameter `report_id` is the ID of the event report in the database.
+    Returns:
+        JSON blob of information about the event report
+    """
+
+    PATTERNS = admin_patterns("/event_reports/(?P<report_id>[^/]*)$")
+
+    def __init__(self, hs):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+
+    async def on_GET(self, request, report_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        message = (
+            "The report_id parameter must be a string representing a positive integer."
+        )
+        try:
+            report_id = int(report_id)
+        except ValueError:
+            raise SynapseError(400, message, errcode=Codes.INVALID_PARAM)
+
+        if report_id < 0:
+            raise SynapseError(400, message, errcode=Codes.INVALID_PARAM)
+
+        ret = await self.store.get_event_report(report_id)
+        if not ret:
+            raise NotFoundError("Event report not found")
+
+        return 200, ret