Add code example for adding a user to a group using group patch API (#625)

## Changes
Added an example of adding a principal to a group using the group patch
API.

## Tests
Tested the code locally.

Author: chrisgravel-db

examples/groups/patch_groups.py

@@ -0,0 +1,24 @@
+import time
+from databricks.sdk import WorkspaceClient
+from databricks.sdk.service import iam
+
+w = WorkspaceClient()
+
+group = w.groups.create(display_name=f'sdk-{time.time_ns()}-group')
+user = w.users.create(
+    display_name=f'sdk-{time.time_ns()}-user', user_name=f'sdk-{time.time_ns()}@example.com')
+
+w.groups.patch(
+    id=group.id,
+    operations=[iam.Patch(
+        op=iam.PatchOp.ADD,
+        value={"members": [{
+            "value": user.id,
+        }]},
+    )],
+    schemas=[iam.PatchSchema.URN_IETF_PARAMS_SCIM_API_MESSAGES_2_0_PATCH_OP],
+)
+
+# cleanup
+w.users.delete(id=user.id)
+w.groups.delete(id=group.id)