NIP-A2: Account delegation via kind-0

A2.md

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+NIP-A2
+======
+
+Account delegation via kind-0
+-------------------
+
+`draft` `optional`
+
+Defines how to use kind-0 for account delegation.
+The clients responsible for account management create and post the delegator kind-0 event.
+A user can utilize the delegatee account listed in their own delegator event. If a user creates a delegatee kind-0 event and it is valid, it is considered to represent the same identity with a different key pair.
+
+## Delegator
+
+```js
+{
+  "kind": 0,
+  "tags": [
+    ["p", <delegatee pubkey>, <approved kind for override>...],
+  ],
+  "content": <metadata>,
+  // ...
+}
+```
+
+- The `p` tag contains the delegatee's pubkey. Optional approved kinds for override can be appended. If no approved kinds are specified, it is considered unrestricted.
+  - MAY have multiple `p` tags.
+
+
+## Delegatee
+
+```js
+{
+  "kind": 0,
+  "tags": [
+    ["P", <delegator pubkey>],
+    ["alt", "delegation account"], // optional
+  ],
+  "content": <empty or metadata override>,
+  // ...
+}
+```
+
+- The `P` tag contains the delegator's pubkey.
+  - MUST NOT have multiple `P` tags.
+- The `content` can be empty or an override of the delegator's metadata if it is approved by the delegator.
+
+## Validation
+
+If a delegator's kind-0 has no `p` tags, and a delegatee's kind-0 contains the delegator's `P` tag, it is considered an invalid delegation, and vice versa.
+
+## Client
+
+Client SHOULD use the delegator's pubkey along with the delegatee's pubkey when adding to or removing from the contact list.
+All delegatee stuff SHOULD be considered an override of the delegator's stuff if each kind is approved by the delegator.
+
+## Example of kind-0 events for delegation
+
+### Delegator
+
+```js
+{
+  "kind": 0,
+  "pubkey": "373ab6e211d2ef30fa72552a072f8cbc6c0cdb72902502d23f05818b6701eaf4",
+  "tags": [
+    ["p", "1d58b9a772e6370e2193ac79055a67f4e2caabd8c9634e07e390ca1b1717946c", 0, 1, 3, 6, 7, 30023],
+  ],
+  "content": "{\"name\":\"User\",\"about\":\"I'm not a bitcoiner\"}",
+  // ...
+}
+```
+
+### Delegatee
+
+```js
+{
+  "kind": 0,
+  "pubkey": "1d58b9a772e6370e2193ac79055a67f4e2caabd8c9634e07e390ca1b1717946c",
+  "tags": [
+    ["P", "373ab6e211d2ef30fa72552a072f8cbc6c0cdb72902502d23f05818b6701eaf4"],
+  ],
+  "content": "{\"name\":\"User (delegatee)\"}",
+  // ...
+}
+```