feat(httpclient)!: promote to v1.0.0 — retry-on-429 with Retry-After, DoJSONRequest, bump deps

Extend retry loop to handle HTTP 429 Too Many Requests: when the server includes a
Retry-After header, that duration is used as the retry delay; otherwise falls back to
the configured BackOffDelay. Add DoJSONRequest[Req, Resp] free function that serialises
the request body as JSON, sets Content-Type, and delegates response decoding to DoJSON.
Bump logz and xerrors from v0.9.0 to v1.0.0. API committed as stable.

httpclient.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"strconv"
 	"time"
 
 	retry "github.com/avast/retry-go/v4"
@@ -91,6 +92,7 @@ func (c *httpClient) Do(req *http.Request) (*http.Response, error) {
 
 	result, err := c.cb.Execute(func() (any, error) {
 		var innerErr error
+		var retryAfterDelay time.Duration
 		retryErr := retry.Do(
 			func() error {
 				if id := logz.GetRequestID(req.Context()); id != "" {
@@ -110,6 +112,14 @@ func (c *httpClient) Do(req *http.Request) (*http.Response, error) {
 					"status", resp.StatusCode,
 					"latency", latency.String(),
 				)
+				if resp.StatusCode == http.StatusTooManyRequests {
+					if ra := resp.Header.Get("Retry-After"); ra != "" {
+						if secs, err := strconv.Atoi(ra); err == nil {
+							retryAfterDelay = time.Duration(secs) * time.Second
+						}
+					}
+					return fmt.Errorf("rate limited: %d", resp.StatusCode)
+				}
 				if resp.StatusCode >= 500 {
 					return fmt.Errorf("server error: %d", resp.StatusCode)
 				}
@@ -117,7 +127,14 @@ func (c *httpClient) Do(req *http.Request) (*http.Response, error) {
 			},
 			retry.Attempts(c.cfg.MaxRetries),
 			retry.Delay(c.cfg.RetryDelay),
-			retry.DelayType(retry.BackOffDelay),
+			retry.DelayType(func(n uint, err error, config *retry.Config) time.Duration {
+				if retryAfterDelay > 0 {
+					d := retryAfterDelay
+					retryAfterDelay = 0
+					return d
+				}
+				return retry.BackOffDelay(n, err, config)
+			}),
 			retry.LastErrorOnly(true),
 		)
 		return resp, retryErr