support user configuration of auth cookie max age

Signed-off-by: Jessica He <jhe@redhat.com>

docs/auth/bitbucketServer/provider.md

@@ -34,6 +34,8 @@ auth:
         host: bitbucket.example.org
         clientId: ${AUTH_BITBUCKET_SERVER_CLIENT_ID}
         clientSecret: ${AUTH_BITBUCKET_SERVER_CLIENT_SECRET}
+        ## uncomment to set lifespan of user session
+        # sessionDuration: { hours: 24 } # supports `ms` library format (e.g. '24h', '2 days'), ISO duration, "human duration" as used in code
 ```
 
 The Bitbucket Server provider is a structure with two configuration keys:
@@ -41,6 +43,10 @@ The Bitbucket Server provider is a structure with two configuration keys:
 - `clientId`: The client ID that was generated by Bitbucket, e.g. `b0f868455c15dcdff5c5fb5d173ae684`.
 - `clientSecret`: The client secret tied to the generated client ID.
 
+### Optional
+
+- `sessionDuration`: Lifespan of the user session.
+
 ### Resolvers
 
 This provider includes several resolvers out of the box that you can use: