Telegram username dupe handling

[chuajunyu]

Fix #79

Changelog

TelegramUsername

• Null Telegram Usernames are still equal to other Null Telegram Usernames. This might seem unintuitive:
  • 1. Because equals recognise null usernames to be different could help us in implementing uniqueness in persons when they both have no telegram username.
  • 2. And also because IRL, you can choose to have no telegram username, but still be a unique user on telegram
  • However, this caused issues in certain test cases which relied on equality checking to check whether the parser is adding the same person (without a telegram username)
  • Additionally, a telegram username on it's own cannot enforce uniqueness, it's a weak notion of identity, so on it's own, even if it's null, it must still be tagged to a unique phone and email.

Person

• Will check if both have telegram username, if either one of them don't, then they will only check for uniqueness in phone and email
• If both have telegram username, then they will check for uniqueness for all phone, email and telegram username.
• Note that the uniqueness is individual, not a tuple

EditCommand

• I simplified some of the code
• There are mainly 2 cases to look out for:
  • 1. When NEW is different from OLD but same as some other person already in the model
  • 2. When NEW is same as OLD and also same as some other person already in the model
  • The old method before Brian updated fails on case b, because it assumes that IF there is a duplicate, and if NEW is same as OLD, then that must be the only duplicate, which is valid. However, there might be another entity in the model with the same phone / email or telegram username
  • To resolve this, I created a new function to count how many duplicates are there in the model
  • I then eliminate case b by adding an extra check to count dupes in the model, the EditCommand is immediately rejected if there are more than 1 duplicates.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...c/main/java/seedu/address/model/person/Person.java	77.77%	0 Missing and 2 partials :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...java/seedu/address/logic/commands/EditCommand.java	97.72% <100.00%> (+2.07%)	14.00 <0.00> (-4.00)	:arrow_up:
src/main/java/seedu/address/model/AddressBook.java	86.11% <100.00%> (+0.81%)	14.00 <1.00> (+1.00)
src/main/java/seedu/address/model/Model.java	100.00% <ø> (ø)	1.00 <0.00> (ø)
...rc/main/java/seedu/address/model/ModelManager.java	100.00% <100.00%> (ø)	26.00 <1.00> (+1.00)
...a/seedu/address/model/person/TelegramUsername.java	89.47% <100.00%> (+6.14%)	12.00 <2.00> (+3.00)
...a/seedu/address/model/person/UniquePersonList.java	88.46% <100.00%> (+0.46%)	23.00 <1.00> (+1.00)
...c/main/java/seedu/address/model/person/Person.java	92.59% <77.77%> (-3.25%)	34.00 <0.00> (+3.00)	:arrow_down: