Showing more user friendly error when the email is already registered

[clacladev]

What does this pull request do? Explain your changes. (required)
Showing more user friendly error when the email is already registered. Also looking for lowercase email when logging in, verifying email and resetting password.

Specific updates (required)

• Looking up for the email (as given and lowercased before registering)
• Registering with 3rd parties and in our DB the lowercase version of the email
• Looking for lowercase email when logging in, verifying email and resetting password.

How did you test each of these updates (required)

• Updated the unit tests
• Run locally the API server and made sure it was passing all the tests
• Manually tested in browser

Does this pull request close any open issues?
Fixes #1531
Fixes #1522

Screenshots:

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Name	Status	Preview	Updated
livepeer-studio	✅ Ready (Inspect)	Visit Preview	Dec 7, 2022 at 6:06PM (UTC)

[codecov]

Codecov Report

Merging #1538 (7cc7ccb) into master (3cddfa5) will increase coverage by 0.05526%.
The diff coverage is 83.33333%.

@@                 Coverage Diff                 @@
##              master       #1538         +/-   ##
===================================================
+ Coverage   53.03197%   53.08723%   +0.05526%     
===================================================
  Files             68          68                 
  Lines           4535        4551         +16     
  Branches         855         860          +5     
===================================================
+ Hits            2405        2416         +11     
- Misses          1820        1825          +5     
  Partials         310         310                 

Impacted Files	Coverage Δ
packages/api/src/controllers/user.ts	42.60355% <83.33333%> (+1.60976%)	⬆️
packages/api/src/store/table.ts	72.61146% <0.00000%> (-0.63695%)	⬇️

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Impacted Files	Coverage Δ
packages/api/src/controllers/user.ts	42.60355% <83.33333%> (+1.60976%)	⬆️
packages/api/src/store/table.ts	72.61146% <0.00000%> (-0.63695%)	⬇️

[adamsoffer]

LGTM