feat: mask cp uid in autoreply to respondent

[tshuli]

Problem

Closes #101

Solution

• Mask UID NRIC before generating autoreply using a function
• To be refactored in Encapsulate the construction and representation of parsed responses into a class #1104

Before & After Screenshots

BEFORE:

AFTER:

Tests

• Create a corppass form with email autoreply and pdf response. Submit form. Check that the autoreply email and pdf response both have a masked UID number with only the last 4 characters shown (e.g. *****123A)
• Add a text field to the form with the title 'CorpPass Validated UID'. Check that the response on the text field is not masked in autoreply.
• Check that the email response to the admin still has the full UID number.

[liangyuanruo]

lgtm, to merge after testing