custom fields: Clean custom fields to use existing defined function.

[YJDave]

Testing Plan:

GIFs or Screenshots:

[YJDave]

Some more observations, should be addressed soon:

• Small fixes required in modal i.e. clear data when add new field,
• In custom fields, "ab" and "ab " are handled as different fields, not sure if this is an issue. We don't compare names with space trim operation I think.
• Proper backend error messages. Currently for any backend error, there is only one message "Name already exist" on integrity error, even if there do not exist any similar name field.

[timabbott]

@YJDave can you fix the Casper tests that failed? They should be changed to check for the new alerts; check some of Shubham Dhama's commits if needed.

[timabbott]

(Otherwise this looks like a really nice cleanup; and I agree with the cleanups).

[YJDave]

Thanks for reviewing! Tests are passing now.

[timabbott]

Merged, thanks @YJDave! I love it when we get to delete code :)