Copy over 0.4.6 release document

releases/0.4.6.md

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+# pict-rs 0.4.6
+
+## Overview
+
+pict-rs 0.4.6 introduces a new internal endpoint to prepare servers for the 0.5.0 upgrade. This is
+to enable the upgrade preparations to be completed on an 0.4 server without taking it offline, thus
+improving the speed at which the upgrade will occur.
+
+### Features
+
+- [Upgrade Preparation Endpoint](#upgrade-preparation-endpoint)
+
+
+### Changes
+
+- [Improved Upload Performance](#improved-upload-performance)
+
+
+## Upgrade Notes
+
+There's no significant changes from 0.4.5, so upgrading should be as simple as pulling a new version
+of pict-rs.
+
+
+## Descriptions
+
+### Upgrade Preparation Endpoint
+
+In pict-rs 0.3 and 0.4, file metadata was automatically extracted from uploads when they were
+created, but earlier versions did not do this. In some scenarios, uploads may be present in pict-rs
+without associated metadata. pict-rs 0.5 introduces a requirement on the presence of this metadata,
+and the upgrade process automatically extracts this information but the upgrade happens before
+pict-rs 0.5 launches its web server, meaning that it will remain inaccessible while it takes the
+time to extract the necessary metadata. 
+
+A new internal endpoint has been introduced at `/internal/prepare_upgrade`. This endpoint will queue
+a job to ensure all uploads pict-rs has handled have associated file metadata. This will improve the
+speed at which the 0.5 upgrade will occur.
+
+The endpoint is available via a `POST` request, and accepts an optional query parameter `force`
+which can be set to `true` in order to force pict-rs to queue the metadata job, even if it has
+already been queued. Generally, force should not be required.
+
+After the endpoint is hit once, any further request to the endpoint without the `force` parameter
+will return the current status of the upgrade preparation job.
+
+Example:
+```bash
+curl \
+    -XPOST \
+    -H'X-APi-Token: api-key' \
+    'http://localhost:8080/internal/prepare_upgrade'
+```
+
+pict-rs will respond with the following json:
+```json
+{
+    "complete": false,
+    "progress": 123,
+    "total": 456
+}
+```
+
+This example indicates that the upgrade preparation has processed 123 uploads out of the total 456,
+and it is not complete. One thing to note is that when the job does complete, the progress value may
+still be less than the total value, although it should be close.
+
+
+### Improved Upload Performance
+
+At the cost of memory, pict-rs will now accept file uploads and read their bytes before a permit for
+external processing becomes available. This improves the speed with which uploads complete, and
+allows clients to fully send their requests without being blocked on other uploads. This also fixes
+a bug where it is possible for malicious clients to hold upload requests open and prevent pict-rs
+from being able to process media.