migrate nips from main nostr repo.

02.md

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+NIP-02
+======
+
+Contact List and Petnames
+-------------------------
+
+`draft` `optional` `author:fiatjaf` `author:arcbtc`
+
+A special event with kind `3`, meaning "contact list" is defined as having a list of `p` tags, one for each of the followed/known profiles one is following.
+
+Each tag entry should contain the key for the profile, a relay URL where events from that key can be found (can be set to `null` or a invalid string if not needed), and a local name (or "petname") for that profile (can also be set to `null`), i.e., `["p", <32-bytes hex key>, <main relay URL>, <petname>]`. The `content` can be anything and should be ignored.
+
+For example:
+
+```json
+{
+  "kind": 3,
+  "tags": [
+    ["p", "91cf9..4e5ca", "wss://alicerelay.com/", "alice"],
+    ["p", "14aeb..8dad4", "wss://bobrelay.com/nostr", "bob"],
+    ["p", "612ae..e610f", "ws://carolrelay.com/ws", "carol"]
+  ],
+  "content": "",
+  ...other fields
+```
+
+Every new contact list that gets published overwrites the past ones, so it should contain all entries. Relays and clients SHOULD delete past contact lists as soon as they receive a new one.
+
+## Uses
+
+### Contact list backup
+
+If one believes a relay will store their events for sufficient time, they can use this kind-3 event to backup their following list and recover on a different device.
+
+### Profile discovery and context augmentation
+
+A client may rely on the kind-3 event to display a list of followed people by profiles one is browsing; make lists of suggestions on who to follow based on the contact lists of other people one might be following or browsing; or show the data in other contexts.
+
+### Relay sharing
+
+A client may publish a full list of contacts with good relays for each of their contacts so other clients may use these to update their internal relay lists if needed, increasing censorship-resistant.
+
+### Petname scheme
+
+The data from these contact lists can be used by clients to construct local ["petname"](http://www.skyhunter.com/marcs/petnames/IntroPetNames.html) tables derived from other people's contact lists. This alleviates the need for global human-readable names. For example:
+
+A user has an internal contact list that says
+
+```json
+[
+  ["p", "21df6d143fb96c2ec9d63726bf9edc71", null, "erin"]
+]
+```
+
+And receives two contact lists, one from `21df6d143fb96c2ec9d63726bf9edc71` that says
+
+```json
+[
+  ["p", "a8bb3d884d5d90b413d9891fe4c4e46d", null, "david"]
+]
+```
+
+and another from `a8bb3d884d5d90b413d9891fe4c4e46d` that says
+
+```json
+[
+  ["p", "f57f54057d2a7af0efecc8b0b66f5708", null, "frank"]
+]
+```
+
+When the user sees `21df6d143fb96c2ec9d63726bf9edc71` the client can show _erin_ instead;
+When the user sees `a8bb3d884d5d90b413d9891fe4c4e46d` the client can show _david.erin_ instead;
+When the user sees `f57f54057d2a7af0efecc8b0b66f5708` the client can show _frank.david.erin_ instead.