Add offline state for pending contacts.

briar-headless/README.md

@@ -131,6 +131,7 @@ This will return a JSON array of pending contacts and their states:
 The state can be one of these values:
 
   * `waiting_for_connection`
+  * `offline`
   * `connecting`
   * `adding_contact`
   * `failed`

briar-headless/src/main/java/org/briarproject/briar/headless/contact/OutputPendingContact.kt

@@ -16,6 +16,7 @@ internal fun PendingContact.output() = JsonDict(
 
 internal fun PendingContactState.output() = when(this) {
     WAITING_FOR_CONNECTION -> "waiting_for_connection"
+    OFFLINE -> "offline"
     CONNECTING -> "connecting"
     ADDING_CONTACT -> "adding_contact"
     FAILED -> "failed"