Update registration conditions to latest code

tips/TIP-0040/tip-0040.md

@@ -104,8 +104,41 @@ IOTA coins and claim their Mana rewards.
 
 ## Registration
 
-Accounts are considered registered for validation if they have a _Staking Feature_ in their _Features_. This feature and
-its transaction validation rules are specified in [TIP-42](../TIP-0042/tip-0042.md).
+Accounts are considered registered as committee candidates for epoch `Candidate Epoch` if they satisfy all of the
+following conditions:
+
+- The account has a [_Staking Feature_](../TIP-0042/tip-0042.md#staking-feature) in their _Features_ where
+  `End Epoch >= Candidate Epoch`.
+- The account issues a block with a _Candidacy Announcement Payload_ before/or in (TODO: Clarify) the
+  `Registration Slot(Candidate Epoch)` as defined in [committee selection](#committee-selection).
+
+### Candidacy Announcement
+
+A _Candidacy Announcement Payload_ does not contain any data as it is only used to signal candidacy. It is serialized as
+follows:
+
+<details>
+  <summary>Candidacy Announcement</summary>
+  <blockquote>Signals candidacy for committee selection for the epoch after the one in which it is issued.</blockquote>
+</details>
+<table>
+  <tr>
+    <td>
+      <b>Name</b>
+    </td>
+    <td>
+      <b>Type</b>
+    </td>
+    <td>
+      <b>Description</b>
+    </td>
+  </tr>
+  <tr>
+    <td>Payload Type</td>
+    <td>uint8</td>
+    <td>Set to <strong>value 2</strong> to denote a <i>Candidacy Announcement Payload</i>.</td>
+  </tr>
+</table>
 
 ## Committee Selection