add keybase unconfined profile

Keybase needs to use user namespaces, hence it needs an unconfined
profile when user namespaces are restricted from unconfined like other
applications in MR #1123

https://gitlab.com/apparmor/apparmor/-/merge_requests/1123

In addition this serves as a handle to uniquely identify keybase
instead of unconfined to peers in policy.

Note that unconfined mode should be changed for default_allow when
https://gitlab.com/apparmor/apparmor/-/merge_requests/1109 is merged.

Signed-off-by: Georgia Garcia <georgia.garcia@canonical.com>

profiles/apparmor.d/keybase

@@ -0,0 +1,12 @@
+# This profile allows everything and only exists to give the
+# application a name instead of having the label "unconfined"
+
+abi <abi/4.0>,
+include <tunables/global>
+
+profile keybase /opt/keybase/Keybase flags=(unconfined) {
+  userns,
+
+  # Site-specific additions and overrides. See local/README for details.
+  include if exists <local/keybase>
+}