refactor: 🔥 Remove Server Actors

app/entities/delete/page.mdx

@@ -13,7 +13,7 @@ Implementations **must** ensure that the author of the `Delete` entity has the a
 
 Having the authorization is defined as:
 - The author is the creator of the target entity (including [delegation](/delegation)).
-- The author is the server actor.
+- The author is the instance.
 
 ## Entity Definition
 
@@ -23,8 +23,8 @@ Having the authorization is defined as:
             <Property name="uri" type="null" required={false}>
                 This entity does not have a URI.
             </Property>
-            <Property name="author" type="URI" required={true} typeLink="/types#uri">
-                URI of the `User` who is deleting the entity.
+            <Property name="author" type="URI | null" required={true} typeLink="/types#uri">
+                URI of the `User` who is deleting the entity. [Can be set to `null` to represent the instance](/entities/server-metadata#the-null-author).
             </Property>
             <Property name="target" type="URI" required={true} typeLink="/types#uri">
                 URI of the entity being deleted.

app/entities/page.mdx

@@ -82,4 +82,4 @@ Any field in an entity not marked as `required` may be omitted or set to `null`.
 When serialized to a string, the JSON representation of an entity should follow the following rules:
 - Keys must be sorted lexicographically.
 - Should use UTF-8 encoding.
-- Must be **signed** using the relevant [User](/entities/user)'s private key, or the [Server Actor](/entities/server-actor)'s private key if the entity is not associated with a particular user.
+- Must be **signed** using the relevant [User](/entities/user)'s private key, or the [instance's private key](/entities/server-metadata) if the entity is not associated with a particular user.

app/entities/server-metadata/page.mdx

@@ -7,12 +7,14 @@ export const metadata = {
 
 Contains metadata about a Versia instance, such as capabilities and endpoints. {{ className: 'lead' }}
 
-Not to be confused with [Server Actor](/entities/server-actor), which is a User representing an instance in the federation.
-
 <Note>
     This entity is only used as part of [Server Discovery](/federation/discovery#server-discovery), and not as part of federation.
 </Note>
 
+## The `null` Author
+
+On all entities that have an `author` field, the `author` can be `null` to represent the instance itself as the author (like ActivityPub's Server Actors). In this case, the instance's public key should be used to verify the entity.
+
 ## Entity Definition
 
 <Row>
@@ -63,6 +65,17 @@ Not to be confused with [Server Actor](/entities/server-actor), which is a User
             <Property name="shared_inbox" type="URI" required={false}>
                 URI to the instance's shared inbox, if supported.
             </Property>
+            <Property name="public_key" type="PublicKey" required={true}>
+                Public key of the instance.
+
+                ```typescript
+                type PublicKey = {
+                    public_key: string;
+                }
+                ```
+
+                - `public_key`: Public key of the instance. Must follow the [Versia Public Key](/signatures) format.
+            </Property>
             <Property name="moderators" type="URI" required={false}>
                 URI to [Collection](/structures/collection) of instance moderators.
 
@@ -120,6 +133,9 @@ Not to be confused with [Server Actor](/entities/server-actor), which is a User
                 "content": "https://social.jimjams.com/files/logo.webp"
             }
         },
+        "public_key": {
+            "public_key": "MCowBQYDK2VwAyEA9zhEMtQZetRl4QrLcz99i7jOa6ZVjX7aLfRUsMuKByI=" 
+        },
         "banner": null,
         "extensions": {
             "example.extension:monthly_active_users": 1000