build(deps): bump github.com/jackc/pgx/v4 from 4.13.0 to 4.15.0

Bumps [github.com/jackc/pgx/v4](https://github.com/jackc/pgx) from 4.13.0 to 4.15.0.
- [Release notes](https://github.com/jackc/pgx/releases)
- [Changelog](https://github.com/jackc/pgx/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jackc/pgx/compare/v4.13.0...v4.15.0)

---
updated-dependencies:
- dependency-name: github.com/jackc/pgx/v4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/jackc/pgconn/config.go

@@ -248,21 +248,21 @@ func ParseConfig(connString string) (*Config, error) {
 	config.LookupFunc = makeDefaultResolver().LookupHost
 
 	notRuntimeParams := map[string]struct{}{
-		"host":                 struct{}{},
-		"port":                 struct{}{},
-		"database":             struct{}{},
-		"user":                 struct{}{},
-		"password":             struct{}{},
-		"passfile":             struct{}{},
-		"connect_timeout":      struct{}{},
-		"sslmode":              struct{}{},
-		"sslkey":               struct{}{},
-		"sslcert":              struct{}{},
-		"sslrootcert":          struct{}{},
-		"target_session_attrs": struct{}{},
-		"min_read_buffer_size": struct{}{},
-		"service":              struct{}{},
-		"servicefile":          struct{}{},
+		"host":                 {},
+		"port":                 {},
+		"database":             {},
+		"user":                 {},
+		"password":             {},
+		"passfile":             {},
+		"connect_timeout":      {},
+		"sslmode":              {},
+		"sslkey":               {},
+		"sslcert":              {},
+		"sslrootcert":          {},
+		"target_session_attrs": {},
+		"min_read_buffer_size": {},
+		"service":              {},
+		"servicefile":          {},
 	}
 
 	for k, v := range settings {
@@ -329,10 +329,19 @@ func ParseConfig(connString string) (*Config, error) {
 		}
 	}
 
-	if settings["target_session_attrs"] == "read-write" {
+	switch tsa := settings["target_session_attrs"]; tsa {
+	case "read-write":
 		config.ValidateConnect = ValidateConnectTargetSessionAttrsReadWrite
-	} else if settings["target_session_attrs"] != "any" {
-		return nil, &parseConfigError{connString: connString, msg: fmt.Sprintf("unknown target_session_attrs value: %v", settings["target_session_attrs"])}
+	case "read-only":
+		config.ValidateConnect = ValidateConnectTargetSessionAttrsReadOnly
+	case "primary":
+		config.ValidateConnect = ValidateConnectTargetSessionAttrsPrimary
+	case "standby":
+		config.ValidateConnect = ValidateConnectTargetSessionAttrsStandby
+	case "any", "prefer-standby":
+		// do nothing
+	default:
+		return nil, &parseConfigError{connString: connString, msg: fmt.Sprintf("unknown target_session_attrs value: %v", tsa)}
 	}
 
 	return config, nil
@@ -727,3 +736,48 @@ func ValidateConnectTargetSessionAttrsReadWrite(ctx context.Context, pgConn *PgC
 
 	return nil
 }
+
+// ValidateConnectTargetSessionAttrsReadOnly is an ValidateConnectFunc that implements libpq compatible
+// target_session_attrs=read-only.
+func ValidateConnectTargetSessionAttrsReadOnly(ctx context.Context, pgConn *PgConn) error {
+	result := pgConn.ExecParams(ctx, "show transaction_read_only", nil, nil, nil, nil).Read()
+	if result.Err != nil {
+		return result.Err
+	}
+
+	if string(result.Rows[0][0]) != "on" {
+		return errors.New("connection is not read only")
+	}
+
+	return nil
+}
+
+// ValidateConnectTargetSessionAttrsStandby is an ValidateConnectFunc that implements libpq compatible
+// target_session_attrs=standby.
+func ValidateConnectTargetSessionAttrsStandby(ctx context.Context, pgConn *PgConn) error {
+	result := pgConn.ExecParams(ctx, "select pg_is_in_recovery()", nil, nil, nil, nil).Read()
+	if result.Err != nil {
+		return result.Err
+	}
+
+	if string(result.Rows[0][0]) != "t" {
+		return errors.New("server is not in hot standby mode")
+	}
+
+	return nil
+}
+
+// ValidateConnectTargetSessionAttrsPrimary is an ValidateConnectFunc that implements libpq compatible
+// target_session_attrs=primary.
+func ValidateConnectTargetSessionAttrsPrimary(ctx context.Context, pgConn *PgConn) error {
+	result := pgConn.ExecParams(ctx, "select pg_is_in_recovery()", nil, nil, nil, nil).Read()
+	if result.Err != nil {
+		return result.Err
+	}
+
+	if string(result.Rows[0][0]) == "t" {
+		return errors.New("server is in standby mode")
+	}
+
+	return nil
+}