Encryption password error: add a note about username casing.

app/src/main/res/values/strings.xml

@@ -221,7 +221,7 @@
 
     <string name="account_creation_failed">Account creation failed</string>
     <string name="wrong_encryption_password">Wrong encryption password</string>
-    <string name="wrong_encryption_password_content">Got an integrity error while accessing your account, which most likely means you put in the wrong encryption password.\n\nError: %s</string>
+    <string name="wrong_encryption_password_content">Got an integrity error while accessing your account, which most likely means you put in the wrong encryption password.\nPlease note that the username is case sensitive, so please also try different capitalizations, for example make the first character uppercase.\n\nError: %s</string>
 
     <!-- ChangeEncryptionPasswordActivity -->
     <string name="change_encryption_password_title">Change Encryption Password</string>