auth_oidc: keep previous value when building authorization_claims (#26565)

src/authentic2_auth_oidc/models.py

@@ -152,11 +152,10 @@ class OIDCProvider(models.Model):
         userinfo_claims = {}
         for claim_mapping in self.claim_mappings.all():
             d = idtoken_claims if claim_mapping.idtoken_claim else userinfo_claims
-            value = {}
+            value = d.setdefault(claim_mapping.claim, {})
             if claim_mapping.required:
                 value['essential'] = True
-            value = value or None
-            d[claim_mapping.claim] = value
+            d[claim_mapping.claim] = value or None
         return {
             'id_token': idtoken_claims,
             'userinfo': userinfo_claims,