Use enum for user redux actions instead of constant value strings

[barnettx]

Problem

Import bloat in src/client/user/actions/index.ts due to actions being stored as constant value strings in src/client/user/actions/types.ts

Closes #937

Solution

Replace constant value strings with UserAction String Enum as suggested in issue.

Tests

npm run build compiled successfully.

First time contributing to this repo, kindly let me if there are areas I can improve in.

[liangyuanruo]

Hi @barnettx ,

Thanks for contributing to the repository!

I've made a suggestion, but the code looks good otherwise. Happy to approve once the changes have been made.

Thanks!

[liangyuanruo]

thanks for your contribution!