🐛 Fix emailer form validation and update endpoint

[aaronleopold]

Resolves #429

The registering of numeric fields was not correct, and so it was parsing them incorrectly triggering the validation error to pop up.

I've taken this as an opportunity to add jest into the frontend app, something that frankly should have been done a LONG time ago. In my spare time, and while developing other features, I'll try to add tests bit by bit to improve overall coverage to reduce small little bugs like this.

Also, the delete emailer functionality (client-side) was never hooked up. So I went ahead and added the hookups

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 46 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
apps/server/src/routers/api/v1/emailer.rs	0.00%	26 Missing ⚠️
core/src/db/entity/emailer/entity.rs	0.00%	13 Missing ⚠️
crates/email/src/emailer.rs	0.00%	7 Missing ⚠️

Files with missing lines	Coverage Δ
core/src/error.rs	0.00% <ø> (ø)
crates/email/src/error.rs	0.00% <ø> (ø)
crates/email/src/emailer.rs	0.00% <0.00%> (ø)
core/src/db/entity/emailer/entity.rs	0.00% <0.00%> (ø)
apps/server/src/routers/api/v1/emailer.rs	0.00% <0.00%> (ø)