Show error messages for adding empty or duplicate items

[Hudamabkhoot]

Description

This update prevents users from adding empty or duplicate items to their list. Users will receive appropriate error messages if they attempt to submit an empty item or an item that already exists in the list, including variations in casing and punctuation.

Related Issue

Closes #10

Acceptance criteria

• Show an error message if the user tries to submit an empty item
• Show an error message if the user tries to submit a new item that is identical to an existing name. For instance, if the list contains apples and the user adds apples.
• Show an error message if the user tries to submit a new item that matches an existing name with punctuation and casing normalized. For instance, if the list contains apples and the user adds aPples or apples, or a pples.
• The user’s original input is saved in the database.

Type of Changes

Enhancement

Updates

Before

After

Testing Steps / QA Criteria

• Do a git checkout jo-hm-check-item-input and git pull.
• Open the homepage by running npm start.
• Navigate to ManageList and attempt to add an empty item, an error message will appear because the input field is required.
• Trying to add an item that already exists will result in an error message.
• Test adding an item with different casing or punctuation from an existing item, it should result in an error message.
• Navigate to List to verify that if the item was not already in the list, it is displayed in the list regardless of error conditions.

[github-actions]

Visit the preview URL for this PR (updated for commit 083c21e):

https://tcl-79-smart-shopping-list--pr28-jo-hm-check-item-inp-iig44emo.web.app

_{(expires Fri, 20 Sep 2024 10:18:20 GMT)}

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[redapy]

Well done, LGTM!