feat: Add MONGO_TLS_CA_CERT env var support for MongoDB TLS

[ferr3ira-gabriel]

Summary

Add support for MONGO_TLS_CA_CERT env var to pass CA certificate to lib-commons MongoDB TLS configuration.

Current State

Midaz uses lib-commons/mongo but does not pass TLS config. It relies on MONGO_PARAMETERS URI string with tlsInsecure=true which skips certificate validation.

Proposed Solution

Add MONGO_TLS_CA_CERT env var (base64 encoded PEM) and pass it to lib-commons:

var tlsCfg *libMongo.TLSConfig
if cfg.MongoTLSCACert != "" {
    tlsCfg = &libMongo.TLSConfig{CACertBase64: cfg.MongoTLSCACert}
}

mongoConnection, err := libMongo.NewClient(ctx, libMongo.Config{
    URI:      mongoSource,
    Database: cfg.MongoDBName,
    TLS:      tlsCfg,
})

This follows the same pattern used for Redis: REDIS_CA_CERT → libRedis.TLSConfig{CACertBase64}

Acceptance Criteria

• Add MONGO_TLS_CA_CERT env var to config struct
• Pass TLS config to lib-commons/mongo NewClient
• Update helm chart to support the new env var
• Works for both onboarding and transaction MongoDB connections