fix: show correct error message for e-service ID validation

[mantariksh]

Problem

Singpass e-service ID validation relies on parsing the HTML of the login page. The login page recently added a semicolon in the line showing the error code, resulting in the FormSG server returning null for the error code. This causes the frontend to show an error message saying "Could not connect SingPass to validate the e-service ID", instead of showing that the e-service ID is invalid.

Solution

Add the semicolon to the parsing code, and also make the comparison case-insensitive.

Screenshots

Before

After

Tests

• Attempt to activate a Singpass form with an invalid e-service ID. The error message should say that Singpass returned error code 138.
• Repeat above test for MyInfo form.

[karrui]

lgtm