Add missing api error

OmiseGO.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name = 'OmiseGO'
-  s.version = '0.9.2'
+  s.version = '0.9.3'
   s.license = 'Apache'
   s.summary = 'The OmiseGO iOS SDK allows developers to easily interact with a node of the OmiseGO eWallet.'
   s.homepage = 'https://omisego.network/'

Source/API/APIError.swift

@@ -37,8 +37,10 @@ public struct APIError {
         case unknownServerError
         case accessTokenNotFound
         case accessTokenExpired
+        case missingIdempotencyToken
         case other(String)
 
+        //swiftlint:disable:next cyclomatic_complexity
         init(code: String) {
             switch code {
             case "client:invalid_parameter":
@@ -59,6 +61,8 @@ public struct APIError {
                 self = .accessTokenNotFound
             case "user:access_token_expired":
                 self = .accessTokenExpired
+            case "client:no_idempotency_token_provided":
+                self = .missingIdempotencyToken
             case let code:
                 self = .other(code)
             }
@@ -88,6 +92,8 @@ public struct APIError {
                 return "user:access_token_not_found"
             case .accessTokenExpired:
                 return "user:access_token_expired"
+            case .missingIdempotencyToken:
+                return "client:no_idempotency_token_provided"
             case .other(let code):
                 return code
             }