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/Chassis/1U/ThermalSubsystem/Fans/CPU2/index.json

@@ -0,0 +1,31 @@
+{
+    "@odata.type": "#Fan.v1_6_0.Fan",
+    "Id": "CPU2",
+    "Name": "Fan for CPU 2",
+    "Status": {
+        "State": "Enabled",
+        "Health": "OK"
+    },
+    "PhysicalContext": "CPU",
+    "Model": "RKS-440DC",
+    "Manufacturer": "Contoso Fans",
+    "PartNumber": "23456-133",
+    "SparePartNumber": "93284-133",
+    "LocationIndicatorActive": false,
+    "HotPluggable": false,
+    "SpeedPercent": {
+        "Reading": 45,
+        "SpeedRPM": 1490,
+        "DataSourceUri": "/redfish/v1/Chassis/1U/Sensors/CPUFan2"
+    },
+    "RatedSpeedRPM": 3300,
+    "Location": {
+        "PartLocation": {
+            "ServiceLabel": "CPU #2 Fan",
+            "LocationType": "Bay",
+            "LocationOrdinalValue": 1
+        }
+    },
+    "@odata.id": "/redfish/v1/Chassis/1U/ThermalSubsystem/Fans/CPU2",
+    "@Redfish.Copyright": "Copyright 2014-2026 DMTF. For the full DMTF copyright policy, see http://www.dmtf.org/about/policies/copyright."
+}