feat: implement 'rewrite' storage middleware (#4146)

docs/content/storage-drivers/middleware/_index.md

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+---
+description: Explains how to use storage middleware
+keywords: registry, on-prem, images, tags, repository, distribution, storage drivers, advanced
+title: Storage middleware
+---
+
+This document describes the registry storage middleware.
+
+## Provided middleware
+
+This storage driver package comes bundled with several middleware options:
+
+- cloudfront
+- redirect
+- [rewrite](rewrite): Partially rewrites the URL returned by the storage driver.

docs/content/storage-drivers/middleware/rewrite.md

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+---
+description: Explains how to use the rewrite storage middleware
+keywords: registry, service, driver, images, storage, middleware, rewrite
+title: Rewrite middleware
+---
+
+A storage middleware which allows to rewrite the URL returned by the storage driver.
+
+For example, it can be used to rewrite the Blob Storage URL returned by the Azure Blob Storage driver to use Azure CDN.
+
+## Parameters
+
+* `scheme`: (optional): Rewrite the returned URL scheme (if set).
+* `host`: (optional): Rewrite the returned URL host (if set).
+* `trimpathprefix` (optional): Trim the prefix from the returned URL path (if set).
+
+## Example configuration
+
+```yaml
+storage:
+  azure:
+    accountname: "ACCOUNT_NAME"
+    accountkey: "******"
+    container: container-name
+middleware:
+  storage:
+    - name: rewrite
+      options:
+        scheme: https
+        host: example-cdn-endpoint.azurefd.net
+        trimpathprefix: /container-name
+```