Contacts allow duplicate emails

[nus-se-script]

While two people in contacts can not have identical names, different people are allowed to have same email addresses. This is not likely to happen, and it is better to be captured.

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_{[original: nus-cs2103-AY2324S2/pe-interim#5569] [original labels: severity.Medium type.FeatureFlaw]}

[ziiqii]

Team's Response

In reality, there are people who share the same company email.

We wanted to accommodate for this case, and impose fewer restrictions on the user.

Duplicate status (if any):

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