### Description

Support mounting to multiple namespaces with the Hashicorp Vault Secrets Back-end

### Use case/motivation

As a data engineer I wish to utilize secrets stored in multiple mount paths (to support connecting to multiple namespaces)  without having to mount to a higher up namespace.

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

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from __future__ import annotations
from unittest import mock
import pytest
from hvac.exceptions import InvalidPath, VaultError
from airflow.providers.hashicorp.secrets.vault import VaultBackend
class TestVaultSecrets:
    @mock.patch("airflow.providers.hashicorp._internal_client.vault_client.hvac")
    def test_get_conn_uri(self, mock_hvac):
        mock_client = mock.MagicMock()
        mock_hvac.Client.return_value = mock_client
        mock_client.secrets.kv.v2.read_secret_version.return_value = {
            "request_id": "94011e25-f8dc-ec29-221b-1f9c1d9ad2ae",
            "lease_id": "",
            "renewable": False,
            "lease_duration": 0,
            "data": {
                "data": {"conn_uri": "postgresql://airflow:airflow@host:5432/airflow"},
                "metadata": {
                    "created_time": "2020-03-16T21:01:43.331126Z",
                    "deletion_time": "",