add PollNoteEvent type

app/src/main/java/com/vitorpamplona/amethyst/service/model/PollNoteEvent.kt

@@ -0,0 +1,76 @@
+package com.vitorpamplona.amethyst.service.model
+
+import com.vitorpamplona.amethyst.model.HexKey
+import com.vitorpamplona.amethyst.model.toHexKey
+import nostr.postr.Utils
+import java.util.Date
+
+class PollNoteEvent(
+    id: HexKey,
+    pubKey: HexKey,
+    createdAt: Long,
+    tags: List<List<String>>,
+    content: String,
+    sig: HexKey
+) : Event(id, pubKey, createdAt, kind, tags, content, sig) {
+    fun mentions() = tags.filter { it.firstOrNull() == "p" }.mapNotNull { it.getOrNull(1) }
+    fun taggedAddresses() = tags.filter { it.firstOrNull() == "a" }.mapNotNull {
+        val aTagValue = it.getOrNull(1)
+        val relay = it.getOrNull(2)
+
+        if (aTagValue != null) ATag.parse(aTagValue, relay) else null
+    }
+
+    fun replyTos() = tags.filter { it.firstOrNull() == "e" }.mapNotNull { it.getOrNull(1) }
+
+    companion object {
+        const val kind = 6969
+
+        fun create(msg: String,
+                   replyTos: List<String>?,
+                   mentions: List<String>?,
+                   addresses: List<ATag>?,
+                   privateKey: ByteArray,
+                   createdAt: Long = Date().time / 1000): PollNoteEvent {
+            val pubKey = Utils.pubkeyCreate(privateKey).toHexKey()
+            val tags = mutableListOf<List<String>>()
+            replyTos?.forEach {
+                tags.add(listOf("e", it))
+            }
+            mentions?.forEach {
+                tags.add(listOf("p", it))
+            }
+            addresses?.forEach {
+                tags.add(listOf("a", it.toTag()))
+            }
+            val id = generateId(pubKey, createdAt, kind, tags, msg)
+            val sig = Utils.sign(id, privateKey)
+            return PollNoteEvent(id.toHexKey(), pubKey, createdAt, tags, msg, sig.toHexKey())
+        }
+    }
+}
+
+/*
+{
+  "id": <32-bytes lowercase hex-encoded sha256 of the serialized event data>
+  "pubkey": <32-bytes lowercase hex-encoded public key of the event creator>,
+  "created_at": <unix timestamp in seconds>,
+  "kind": 6969,
+  "tags": [
+    ["e", <32-bytes hex of the id of the poll event>, <primary poll host relay URL>],
+    ["p", <32-bytes hex of the key>, <primary poll host relay URL>],
+    ["poll_options",
+        "[[0, 'poll option 0 description string'],
+        [1, 'poll option 1 description string'],
+        [<n>, 'poll option <n> description string']]"
+    ],
+    ["value_maximum", "maximum satoshi value for inclusion in tally"],
+    ["value_minimum", "minimum satoshi value for inclusion in tally"],
+    ["consensus_threshold", "required percentage to attain consensus <0..100>"],
+    ["closed_at", "unix timestamp in seconds"],
+  ],
+  "ots": <base64-encoded OTS file data>
+  "content": <primary poll description string>,
+  "sig": <64-bytes hex of the signature of the sha256 hash of the serialized event data, which is the same as the "id" field>
+}
+ */