Added a genre enum to the user model and a custom validation

[kmilodenisglez]

Signed-off-by: Kmilo Denis Glez [email protected]

Fixes Or Enhances

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• [x] Tests exist or have been written that cover this particular change.

@go-playground/validator-maintainers

[coveralls]

Coverage remained the same at 74.182% when pulling 42127e57b684d077a344608d72474067d6c8c015 on kmilodenisglez:struct-level-updated into c7e0172e0fd176bdc521afb5186818a7db6b77ac on go-playground:master.

[kmilodenisglez]

Updated the Struct Level Example