Describe the bug
OpenSearch Dashboards encodes useful state in the hash component of the URL, for example:

https://<domain>/app/discover#/?_a=(columns:!(level,loggerCategory,messageText,shardName,tags.subDir,workspaceId))

Currently, the SAML component's nextUrl builder includes url.path but omits url.hash, dropping this state. This creates a problem when sharing links to a particular view without first creating a shortlink, in that the state of that view is lost. For the example above, the redirect would be:

https://<domain>/auth/saml/login?nextUrl=%2Fapp%2Fdiscover

and after authentication, the user would land at:

https://<domain>/app/discover

With no preselected columns.

Expected behavior
I believe the user expect to be redirected back to the exact URL, including hash, as they were at before the authentication redirect. I believe it would be preferable to include url.hash, so the nextUrl would become:

https://<domain>/auth/saml/login?nextUrl=%2Fapp%2Fdiscover%23%2F%3F_a%3D%28columns%3A%21%28level%2CloggerCategory%2CmessageText%2CshardName%2Ctags.subDir%2CworkspaceId%29%29

Additional context

• security-dashboards-plugin/server/auth/types/saml/saml_auth.ts

  Line 57 in afd6497

  (request.url.path || '/app/opensearch-dashboards');

• https://nodejs.org/dist/latest-v8.x/docs/api/url.html#url_url_strings_and_url_objects
• https://www.elastic.co/guide/en/kibana/master/kibana-navigation.html#state-sync