Adding upstream version 2.52.6.

Signed-off-by: Daniel Baumann <daniel@debian.org>

docs/api/middleware/idempotency.md

@@ -0,0 +1,83 @@
+---
+id: idempotency
+---
+
+# Idempotency
+
+Idempotency middleware for [Fiber](https://github.com/gofiber/fiber) allows for fault-tolerant APIs where duplicate requests — for example due to networking issues on the client-side — do not erroneously cause the same action performed multiple times on the server-side.
+
+Refer to https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-idempotency-key-header-02 for a better understanding.
+
+## Signatures
+
+```go
+func New(config ...Config) fiber.Handler
+```
+
+## Examples
+
+Import the middleware package that is part of the Fiber web framework
+
+```go
+import (
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/idempotency"
+)
+```
+
+After you initiate your Fiber app, you can use the following possibilities:
+
+### Default Config
+
+```go
+app.Use(idempotency.New())
+```
+
+### Custom Config
+
+```go
+app.Use(idempotency.New(idempotency.Config{
+	Lifetime: 42 * time.Minute,
+	// ...
+}))
+```
+
+### Config
+
+| Property            | Type                    | Description                                                                              | Default                        |
+|:--------------------|:------------------------|:-----------------------------------------------------------------------------------------|:-------------------------------|
+| Next                | `func(*fiber.Ctx) bool` | Next defines a function to skip this middleware when returned true.                      | A function for safe methods    |
+| Lifetime            | `time.Duration`         | Lifetime is the maximum lifetime of an idempotency key.                                  | 30 * time.Minute               |
+| KeyHeader           | `string`                | KeyHeader is the name of the header that contains the idempotency key.                   | "X-Idempotency-Key"            |
+| KeyHeaderValidate   | `func(string) error`    | KeyHeaderValidate defines a function to validate the syntax of the idempotency header.   | A function for UUID validation |
+| KeepResponseHeaders | `[]string`              | KeepResponseHeaders is a list of headers that should be kept from the original response. | nil (keep all headers)         |
+| Lock                | `Locker`                | Lock locks an idempotency key.                                                           | An in-memory locker            |
+| Storage             | `fiber.Storage`         | Storage stores response data by idempotency key.                                         | An in-memory storage           |
+
+## Default Config
+
+```go
+var ConfigDefault = Config{
+	Next: func(c *fiber.Ctx) bool {
+		// Skip middleware if the request was done using a safe HTTP method
+		return fiber.IsMethodSafe(c.Method())
+	},
+
+	Lifetime: 30 * time.Minute,
+
+	KeyHeader: "X-Idempotency-Key",
+	KeyHeaderValidate: func(k string) error {
+		if l, wl := len(k), 36; l != wl { // UUID length is 36 chars
+			return fmt.Errorf("%w: invalid length: %d != %d", ErrInvalidIdempotencyKey, l, wl)
+		}
+
+		return nil
+	},
+
+	KeepResponseHeaders: nil,
+
+	Lock: nil, // Set in configDefault so we don't allocate data here.
+
+	Storage: nil, // Set in configDefault so we don't allocate data here.
+}
+```