feat: ✨ Add version discovery system

app/api/basics/page.mdx

@@ -65,6 +65,7 @@ This is forbidden:
 ```http
 GET /.versia/v0.6/entities/user/1234
 Host: example.com
+Accept: application/vnd.versia+json
 
 HTTP/1.1 301 Moved Permanently
 Location: https://example.com/users/1234
@@ -74,7 +75,8 @@ This is allowed:
 ```http
 GET /.versia/v0.6/entities/user/1234
 Host: example.com
+Accept: text/html
 
 HTTP/1.1 301 Moved Permanently
-Location: https://example.com/.versia/v0.6/entities/user/1234
+Location: https://example.com/users/1234
 ```

app/api/endpoints/page.mdx

@@ -5,6 +5,58 @@ export const metadata = {
 
 # Endpoints
 
+## Well-known
+
+<Warning>
+    This endpoint is exempt from the signature requirement. No signatures are required for requests or responses to it.
+
+    The following `Accept` headers are also allowed for requests to this endpoint:
+    - `application/jrd+json`
+    - `application/json`
+</Warning>
+
+<Row>
+  <Col>
+
+    <Properties name="Well-known">
+        <Property name="endpoint">
+            Must be `/.well-known/versia`.
+        </Property>
+        <Property name="method">
+            Must be `GET`.
+        </Property>
+        <Property name="response">
+            A small JSON object with a single attribute:
+
+            - `versions`: Supported Versia Protocol versions.
+                  - Versions marked as "Working Draft X" are represented as `0.X`.
+        </Property>
+    </Properties>
+
+  </Col>
+  <Col sticky>
+
+    ```http {{ 'title': 'Example request' }}
+    GET /.well-known/versia
+    Host: b.social
+    Accept: application/jrd+json
+    ```
+    
+    ```http {{ 'title': 'Example response' }}
+    HTTP/1.1 200 OK
+    Content-Type: application/jrd+json
+
+    {
+        "versions": [
+            "0.6.0",
+            "0.5.0"
+        ]
+    }
+    ```
+
+  </Col>
+</Row>
+
 ## Instance metadata
 
 <Warning>

app/changelog/page.mdx

@@ -11,8 +11,10 @@ This page lists changes since Working Draft 3. {{ className: 'lead' }}
 ## Since WD 5
 
 - Added a new `content-type` for Versia entities: `application/vnd.versia+json`.
+- Overhauled the Instance-to-Instance API to have clearly defined and namespaced endpoints, under `/.versia/v0.6/`, instead of letting implementations define their own endpoints.
 - Removed per-User keypairs: now, only the instance keypair is used for signing.
 - Moved [Delegation](/extensions/delegation) to an extension
+- Changed the contents of the [Well-Known Versia Endpoint](/api/endpoints#well-known) to only list supported protocol versions.
 - Modified how URIs and references to other entities are handled:
     - The `uri` field has been removed from all entities.
     - Every field that used to be a URI now uses that entity's `id` field.

app/federation/discovery/page.mdx

@@ -49,11 +49,32 @@ Accept: application/jrd+json
 
 ## Instance Discovery
 
-Instance metadata can be accessed by making a `GET` request to the instance's Versia metadata endpoint, documented in the [Endpoints](/api/endpoints#instance-metadata) document.
+Instance metadata can be accessed in two steps:
+
+1. Making a `GET` request to the instance's [`/.well-known/versia` endpoint](/api/endpoints#well-known) to discover supported Versia Protocol versions.
+2. Picking a protocol version to use, and then querying the instance metadata endpoint as documented in the [Endpoints](/api/endpoints#instance-metadata) document.
 
 ### Example
 
-To discover the metadata of the instance `versia.social`, an instance would make a `GET` request to `https://versia.social/.versia/v0.6/instance`.
+To discover the metadata of the instance `versia.social`, an instance would first make a `GET` request to `https://versia.social/.well-known/versia`.
+
+```http {{ 'title': 'Example Request' }}
+GET /.well-known/versia HTTP/1.1
+Accept: application/json
+```
+
+```jsonc {{ 'title': 'Example Response' }}
+{
+    "versions": [
+        "0.6.0",
+        "0.5.0"
+    ]
+}
+```
+
+Then, we
+- Pick version `0.6.0` to use
+- Make a `GET` request to `https://versia.social/.versia/v0.6/instance`.
 
 This endpoint will return an [InstanceMetadata](/entities/instance-metadata) entity.
 
@@ -72,7 +93,8 @@ Accept: application/vnd.versia+json
     },
     "compatibility": {
         "versions": [
-            "0.5.0"
+            "0.5.0",
+            "0.6.0"
         ],
         "extensions": [
             "pub.versia:reactions",

components/Navigation.tsx

@@ -275,9 +275,6 @@ export const navigation: NavGroup[] = [
         links: [
             { title: "Basics", href: "/api/basics" },
             { title: "Endpoints", href: "/api/endpoints" },
-            { title: "Rate Limits", href: "/api/rate-limits" },
-            { title: "Errors", href: "/api/errors" },
-            { title: "HTML Redirects", href: "/api/html" },
         ],
     },
     {