[ELY-2374] Add support domain_hint query parameter

Azure AD allows to pass the domain_hint parameter to the /authorize
endpoint which helps user account selection (see https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-auth-code-flow#request-an-authorization-code).
This commit adds support for appending this parameter to the redirect
uri.

http/oidc/src/main/java/org/wildfly/security/http/oidc/Oidc.java

@@ -62,6 +62,7 @@ public class Oidc {
     public static final String ERROR = "error";
     public static final String GRANT_TYPE = "grant_type";
     public static final String LOGIN_HINT = "login_hint";
+    public static final String DOMAIN_HINT = "domain_hint";
     public static final String MAX_AGE = "max_age";
     public static final String PASSWORD = "password";
     public static final String PROMPT = "prompt";

http/oidc/src/main/java/org/wildfly/security/http/oidc/OidcRequestAuthenticator.java

@@ -21,6 +21,7 @@
 import static org.wildfly.security.http.oidc.ElytronMessages.log;
 import static org.wildfly.security.http.oidc.Oidc.CLIENT_ID;
 import static org.wildfly.security.http.oidc.Oidc.CODE;
+import static org.wildfly.security.http.oidc.Oidc.DOMAIN_HINT;
 import static org.wildfly.security.http.oidc.Oidc.ERROR;
 import static org.wildfly.security.http.oidc.Oidc.KC_IDP_HINT;
 import static org.wildfly.security.http.oidc.Oidc.LOGIN_HINT;
@@ -163,7 +164,7 @@ protected String getRedirectUri(String state) {
                 url = uriBuilder.build().toString();
             }
 
-            List<String> forwardableQueryParams = Arrays.asList(LOGIN_HINT, KC_IDP_HINT, PROMPT, MAX_AGE, UI_LOCALES, SCOPE);
+            List<String> forwardableQueryParams = Arrays.asList(LOGIN_HINT, DOMAIN_HINT, KC_IDP_HINT, PROMPT, MAX_AGE, UI_LOCALES, SCOPE);
             List<NameValuePair> forwardedQueryParams = new ArrayList<>(forwardableQueryParams.size());
             for (String paramName : forwardableQueryParams) {
                 String paramValue = getQueryParamValue(facade, paramName);