Initial service implementation for using a PIN code. (#1912)

* Initial service implementation for using a PIN code.

* Tweak Danger for commit size

600-800 lines is perfectly normal for our PRs, up it to 1000.

ElementX/Sources/Services/Keychain/KeychainControllerProtocol.swift

@@ -24,9 +24,24 @@ struct KeychainCredentials {
 
 // sourcery: AutoMockable
 protocol KeychainControllerProtocol: ClientSessionDelegate {
+    // MARK: Restoration Tokens
+    
     func setRestorationToken(_ restorationToken: RestorationToken, forUsername: String)
     func restorationTokenForUsername(_ username: String) -> RestorationToken?
     func restorationTokens() -> [KeychainCredentials]
     func removeRestorationTokenForUsername(_ username: String)
     func removeAllRestorationTokens()
+    
+    // MARK: App Secrets
+    
+    /// Removes everything from the keychain excluding any restoration tokens.
+    func resetSecrets()
+    /// Whether or not an App Lock PIN code has been set.
+    func containsPINCode() throws -> Bool
+    /// Sets a new PIN code for App Lock.
+    func setPINCode(_ pinCode: String) throws
+    /// The PIN code required to unlock the app.
+    func pinCode() -> String?
+    /// Removes the App Lock PIN code.
+    func removePINCode()
 }