Add DMTF mockup fixtures and test helpers

Unmodified files from DMTF Redfish-Publications (public-rackmount1, public-localstorage, public-telemetry), only those the tests use, each set with DMTF's BSD-3-Clause license and a COMMANDS.txt naming the source commit and request paths.

conftest.py loads them by request path and serves a mockup over mocked HTTP, with a SessionService that hands out a token, for the transport tests.

tests/fixtures/dmtf-public-rackmount1/Managers/BMC/LogServices/Log/Entries/index.json

@@ -0,0 +1,30 @@
+{
+    "@odata.type": "#LogEntryCollection.LogEntryCollection",
+    "Name": "Log Service Collection",
+    "Description": "Collection of Logs for this System",
+    "Members@odata.count": 1,
+    "Members": [
+        {
+            "@odata.id": "/redfish/v1/Managers/BMC/LogServices/Log/Entries/1",
+            "@odata.type": "#LogEntry.v1_22_0.LogEntry",
+            "Id": "1",
+            "Name": "Log Entry 1",
+            "EntryType": "Event",
+            "Severity": "Critical",
+            "Created": "2012-03-07T14:44:00Z",
+            "SensorNumber": 1,
+            "Message": "System May be Melting",
+            "MessageId": "Event.1.0.TempWayTooHot",
+            "MessageArgs": [
+                "88"
+            ],
+            "Links": {
+                "OriginOfCondition": {
+                    "@odata.id": "/redfish/v1/Chassis/1U/Thermal"
+                }
+            }
+        }
+    ],
+    "@odata.id": "/redfish/v1/Managers/BMC/LogServices/Log/Entries",
+    "@Redfish.Copyright": "Copyright 2014-2026 DMTF. For the full DMTF copyright policy, see http://www.dmtf.org/about/policies/copyright."
+}