Docs: Datasource uid docs (#23700)

docs/sources/administration/provisioning.md

@@ -93,6 +93,8 @@ datasources:
   access: proxy
   # <int> org id. will default to orgId 1 if not specified
   orgId: 1
+  # <string> custom UID which can be used to reference this datasource in other parts of the configuration, if not specified will be generated automatically
+  uid: my_unique_uid
   # <string> url
   url: http://localhost:8080
   # <string> Deprecated, use secureJsonData.password

docs/sources/features/datasources/loki.md

@@ -189,8 +189,15 @@ datasources:
     jsonData:
       maxLines: 1000
       derivedFields:
-        - datasourceName: Jaeger
+        # Field with internal link pointing to datasource in Grafana
+        - datasourceUid: my_jaeger_uid
           matcherRegex: "traceID=(\\w+)"
+          name: TraceID
+          # url will be interpreted as query for the datasource
+          url: "$${__value.raw}"
+
+        # Field with external link
+        - matcherRegex: "traceID=(\\w+)"
           name: TraceID
           url: "http://localhost:16686/trace/$${__value.raw}"
 ```