TF-46 Create object, builder for model and core module

model/lib/email/email_action_type.dart

@@ -0,0 +1,7 @@
+
+enum EmailActionType {
+  reply,
+  forward,
+  replyAll,
+  compose,
+}

model/lib/email/prefix_email_address.dart

@@ -0,0 +1,6 @@
+
+enum PrefixEmailAddress {
+  to,
+  cc,
+  bcc
+}

model/lib/email/presentation_email.dart

@@ -53,7 +53,7 @@ class PresentationEmail with EquatableMixin {
 
   String getAvatarText() {
     if (getSenderName().isNotEmpty) {
-      return getSenderName().substring(0, 1).toUpperCase();
+      return getSenderName()[0].toUpperCase();
     }
     return '';
   }