SQL Connect errors are hard to debug in autosetup with Postgres

[pquerna]

Expected Behavior

When SQL connection is misconfigured, show a more accurate error message.

Actual Behavior

I had misconfigured TLS client certificates when using the autosetup container, using Postgres

This was difficult to debug, because the container would log like this:

+ SCHEMA_DIR=/etc/temporal/schema/postgresql/v96/temporal/versioned
+ temporal-sql-tool --plugin postgres --ep 127.0.0.1 -u postgres -p 5432 create --db temporal
2021/05/27 21:22:03 error creating database:unable to connect to DB, tried default DB names: postgres,defaultdb

Steps to Reproduce the Problem

When temporal-sql-tool is invoked with create, it sets the DatabaseName to "", and then invokes tryConnect/sqlx.Connect:

temporal/common/persistence/sql/sqlplugin/postgresql/plugin.go

Lines 117 to 138 in 2e3332f

	func (d *plugin) tryConnect(
	cfg *config.SQL,
	r resolver.ServiceResolver,
	) (*sqlx.DB, error) {
	if cfg.DatabaseName != "" {
	return sqlx.Connect(PluginName, buildDSN(cfg, r))
	}
	// database name not provided
	// try defaults
	defer func() { cfg.DatabaseName = "" }()
	for _, databaseName := range defaultDatabaseNames {
	cfg.DatabaseName = databaseName
	if sqlxDB, err := sqlx.Connect(PluginName, buildDSN(cfg, r)); err == nil {
	return sqlxDB, nil
	}
	}
	return nil, serviceerror.NewInternal(
	fmt.Sprintf("unable to connect to DB, tried default DB names: %v", strings.Join(defaultDatabaseNames, ",")),
	)
	}

Errors from the loop of trying different default DB names are ignored - instead a static string error is returned. Ideally this message would also include the Last error (or all of the errors) -- this would of made it more obvious I had misconfigured TLS.

[pquerna]

Looks like change was recently changed via #1413