Add SSL support for backend connections in PGSQL monitor

[rahim-kanji]

PostgreSQL monitor now supports client certificates for SSL/TLS connections to backend servers.

• Added two new metrics, PgSQL_Monitor_ssl_connections_OK and PgSQL_Monitor_non_ssl_connections_OK (in stats_pgsql_global), to improve visibility into PostgreSQL monitor connection status.

Closes #5205

[gemini-code-assist]

Summary of Changes

Hello @rahim-kanji, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly upgrades the PostgreSQL monitor's capabilities by integrating robust SSL/TLS client certificate support for connections to backend servers. This enhancement allows for more secure and authenticated communication channels, addressing the need for stronger encryption and identity verification in database monitoring.

Highlights

• SSL Options Structure: Introduced a new ssl_opts_t structure within mon_srv_t to hold client certificate, key, CA, and CRL paths for secure PostgreSQL backend connections.
• Configuration Loading: Updated the ext_srvs function to load and populate these new SSL options from global configuration variables when fetching server details.
• Secure Connection String Building: Enhanced the build_conn_str function to dynamically construct the PostgreSQL connection string, incorporating sslmode='require' and the specified client certificate parameters if SSL is enabled for a server.
• Parameter Escaping Utility: Added a new helper function append_conninfo_param to safely append connection parameters to the connection string, ensuring proper escaping of special characters.

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[gemini-code-assist]

Code Review

This pull request adds SSL support for backend connections in the PostgreSQL monitor by extending the server configuration with SSL options and updating the connection string builder. The overall approach is sound, but there's a critical compilation error in how the new SSL options are initialized. I've also included a suggestion to optimize the new helper function for building connection string parameters.

[renecannao]

@rahim-kanji : we should add some TAP test , at least to verify that SSL is being used for monitoring

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud