Allow duplicated Phone Number

[nus-se-script]

As shown in the screenshot below, inserting same phone number for different person is allowed, which is not supposed to be in real-world scenario. In real-world scenario, no more than one person should have the same phone number and phone number should be unique.

As shown below, different person were added with the same phone number, and the program allows it. (Client Index 7, 8 and 9)

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_{[original: nus-cs2103-AY2324S2/pe-interim#388] [original labels: severity.Low type.FeatureFlaw]}

[chewbum]

Team's Response

No details provided by team.

Duplicate status (if any):

Duplicate of #299