I have not started any script yet but wanted to check first If this can be achieved to configure Azure AD Non gallery enterprise app using PowerShell that let me enter metadata such as entity id, reply URL, sign-on URL and attributes information.
I need a suggestion to start on this If you could shed some lights?
For powershell, this is not currently possible. In May, Microsoft added the ServicePrincipals endpoint to 1.0 graph api for (enterprise applications). So using graph api, you may be able to accomplish it. I know until very recently this was still not possible, however checking today the updateserviceprincipal endpoint seem to have the replyurls attributes and loginurl and the serviceprincipalnames (entityid?) So there is a good chance you could get it to work using graph api. but you may have to use the beta graph endpoint.
I would use this endpoint to create the application: https://learn.microsoft.com/en-us/graph/api/applicationtemplate-instantiate?view=graph-rest-beta&tabs=http I believe the custom basic saml app template id is : 8adf8e6e-67b2-4cf2-a259-e3dc5476c621
after creating it. you would need to find the service principal objectid and set the signinmode to saml:
Here are all the necessary calls and example. https://learn.microsoft.com/en-us/azure/active-directory/manage-apps/application-saml-sso-configure-api#step-2-configure-single-sign-on
