feat(prebuilt/alloydb-postgres): support ipType and IAM users (#1324)

## Description
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> Should include a concise description of the changes (bug or feature),
it's
> impact, along with a summary of the solution

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- [ ] Make sure to open an issue as a

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🛠️ Fixes #<issue_number_goes_here>

docs/en/reference/prebuilt-tools.md

@@ -19,8 +19,10 @@ See guides, [Connect from your IDE](../how-to/connect-ide/_index.md), for detail
     *   `ALLOYDB_POSTGRES_CLUSTER`: The ID of your AlloyDB cluster.
     *   `ALLOYDB_POSTGRES_INSTANCE`: The ID of your AlloyDB instance.
     *   `ALLOYDB_POSTGRES_DATABASE`: The name of the database to connect to.
-    *   `ALLOYDB_POSTGRES_USER`: The database username.
-    *   `ALLOYDB_POSTGRES_PASSWORD`: The password for the database user.
+    *   `ALLOYDB_POSTGRES_USER`: The database username. Defaults to IAM authentication if unspecified.
+    *   `ALLOYDB_POSTGRES_PASSWORD`: The password for the database user. Defaults to IAM authentication if unspecified.
+    *   `ALLOYDB_POSTGRES_IP_TYPE`: The IP type i.e. "Public
+     or "Private" (Default: Public).
 *   **Permissions:**
     *   **AlloyDB Client** (`roles/alloydb.client`) to connect to the instance.
     *   Database-level permissions (e.g., `SELECT`, `INSERT`) are required to execute queries.

internal/prebuiltconfigs/tools/alloydb-postgres.yaml

@@ -1,3 +1,16 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 sources:
     alloydb-pg-source:
         kind: "alloydb-postgres"
@@ -6,8 +19,9 @@ sources:
         cluster: ${ALLOYDB_POSTGRES_CLUSTER}
         instance: ${ALLOYDB_POSTGRES_INSTANCE}
         database: ${ALLOYDB_POSTGRES_DATABASE}
-        user: ${ALLOYDB_POSTGRES_USER}
-        password: ${ALLOYDB_POSTGRES_PASSWORD}
+        user: ${ALLOYDB_POSTGRES_USER:}
+        password: ${ALLOYDB_POSTGRES_PASSWORD:}
+        ipType: ${ALLOYDB_POSTGRES_IP_TYPE:public}
 
 tools:
     execute_sql:
@@ -92,7 +106,7 @@ tools:
                         'constraints', COALESCE((SELECT json_agg(json_build_object('constraint_name',cons.constraint_name,'constraint_type',cons.constraint_type,'constraint_definition',cons.constraint_definition,'constraint_columns',cons.constraint_columns,'foreign_key_referenced_table',cons.foreign_key_referenced_table,'foreign_key_referenced_columns',cons.foreign_key_referenced_columns)) FROM constraints_info cons WHERE cons.table_oid = ti.table_oid), '[]'::json),
                         'indexes', COALESCE((SELECT json_agg(json_build_object('index_name',ii.index_name,'index_definition',ii.index_definition,'is_unique',ii.is_unique,'is_primary',ii.is_primary,'index_method',ii.index_method,'index_columns',ii.index_columns)) FROM indexes_info ii WHERE ii.table_oid = ti.table_oid), '[]'::json),
                         'triggers', COALESCE((SELECT json_agg(json_build_object('trigger_name',tri.trigger_name,'trigger_definition',tri.trigger_definition,'trigger_enabled_state',tri.trigger_enabled_state)) FROM triggers_info tri WHERE tri.table_oid = ti.table_oid), '[]'::json)
-                    ) 
+                    )
                 END AS object_details
             FROM table_info ti ORDER BY ti.schema_name, ti.table_name;
         parameters: