Create a key for ceph-osd for crash module auth

This will be set on the osd relation,
so the ceph-osd charm can use this key for auth
by the crash reporting module.

ref. https://docs.ceph.com/en/latest/mgr/crash/

See https://review.opendev.org/c/openstack/charm-ceph-osd/+/869139
for how this key is used by ceph-osd.

Closes-Bug: #2000630
Change-Id: Ic95aae6b5981a6df1e0b3c310bcef8018c494a24

src/ceph_hooks.py

@@ -839,6 +839,16 @@ def osd_relation(relid=None, unit=None):
                         'allow command "osd destroy"',
                     ]
                 }
+            ),
+            # Provide a key to the osd for use by the crash module:
+            # https://docs.ceph.com/en/latest/mgr/crash/
+            'client_crash_key': ceph.create_named_keyring(
+                'client',
+                'crash',
+                caps={
+                    'mon': ['profile crash'],
+                    'mgr': ['profile crash'],
+                }
             )
         }