FINERACT-1222: Add Swagger tags for Notifications

[elicsmit]

Description

This PR adds missing Swagger API documentation tags and operation summaries for the Notification functional area. This is part of the task FINERACT-1222. To ensure a better review process, I have decomposed the changes into smaller parts, and this Pull Request specifically focuses on the notification package.

Checklist

Please make sure these boxes are checked before submitting your pull request - thanks!

• Write the commit message as per our guidelines
• Acknowledge that we will not review PRs that are not passing the build ("green") - it is your responsibility to get a proposed PR to pass the build, not primarily the project's maintainers.
• Create/update unit or integration tests for verifying the changes made.
• Follow our coding conventions.
• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
• This PR must not be a "code dump". Large changes can be made in a branch, with assistance. Ask for help on the developer mailing list.