fix: added error messages, response messages to event route-Team-D chineduMbaodoh-dev

[nitoC]

Pull Request Description

added error messages, response messages to event route also created a custom message for update event in constant.js file

Changes Made

• added the custom error message to catch blocks in event controller in the event.js file.
• created a custom error message for server error 500.
• add response messages from constant.js in the event controller

Checklist

• [ ] I have tested these changes locally and they work as expected.
• [ ] I have updated the documentation, if necessary.
• [ ] My code follows the project's coding standards and style guidelines.
• [ ] I have added appropriate comments to my code, especially in complex or unclear areas.
• [ ] I have requested reviews from team members.
• [ ] I have resolved any merge conflicts.
• [ ] I understand that these changes may affect other parts of the codebase and have taken that into account.

Checklist for Reviewers

[Include a checklist of items for reviewers to verify or test.]

• [ ] The code changes meet the project's coding standards and style guidelines.
• [ ] The changes resolve the issue or implement the feature described.
• [ ] The code is well-documented and includes comments where necessary.
• [ ] Any new dependencies or libraries are necessary and properly documented.
• [ ] The changes have been tested and work as expected.