refactor(oauth): make WithTenant extensible with authority types

apps/internal/oauth/ops/authority/authority.go

@@ -235,23 +235,24 @@ func NewAuthParams(clientID string, authorityInfo Info) AuthParams {
 //   - the client is configured to authenticate only Microsoft accounts via the "consumers" endpoint
 //   - the resulting authority URL is invalid
 func (p AuthParams) WithTenant(ID string) (AuthParams, error) {
-	switch ID {
-	case "", p.AuthorityInfo.Tenant:
-		// keep the default tenant because the caller didn't override it
+	if ID == "" || ID == p.AuthorityInfo.Tenant {
 		return p, nil
-	case "common", "consumers", "organizations":
-		if p.AuthorityInfo.AuthorityType == AAD {
+	}
+
+	var authority string
+	switch p.AuthorityInfo.AuthorityType {
+	case AAD:
+		if ID == "common" || ID == "consumers" || ID == "organizations" {
 			return p, fmt.Errorf(`tenant ID must be a specific tenant, not "%s"`, ID)
 		}
-		// else we'll return a better error below
-	}
-	if p.AuthorityInfo.AuthorityType != AAD {
-		return p, errors.New("the authority doesn't support tenants")
-	}
-	if p.AuthorityInfo.Tenant == "consumers" {
-		return p, errors.New(`client is configured to authenticate only personal Microsoft accounts, via the "consumers" endpoint`)
+		if p.AuthorityInfo.Tenant == "consumers" {
+			return p, errors.New(`client is configured to authenticate only personal Microsoft accounts, via the "consumers" endpoint`)
+		}
+		authority = "https://" + path.Join(p.AuthorityInfo.Host, ID)
+	case ADFS:
+		return p, errors.New("ADFS authority doesn't support tenants")
 	}
-	authority := "https://" + path.Join(p.AuthorityInfo.Host, ID)
+
 	info, err := NewInfoFromAuthorityURI(authority, p.AuthorityInfo.ValidateAuthority, p.AuthorityInfo.InstanceDiscoveryDisabled)
 	if err == nil {
 		info.Region = p.AuthorityInfo.Region