Relay allowlist column added

What does this MR do and why?

MR is a part solution for Issue #410062 (closed)

Relay allowlist column added

This MR adds new column for storing allowed domain list for Relay state parameter. Relay state is sent from SAML Idp end for application to know where to redirect user.

Steps to reproduce

1. Run migration rake db:migrate
2. Verify a new column is added to the tables ApplicationSettings and SamlProviders

Migration Logs

Rollback logs