Add functionality to expense group creation/management

[Mari618]

User Story: Users can create and manage expense groups with detailed attributes

**As a user, I want to create and manage expense groups, so that I can organize and track my budget and expenses more effectively.

Acceptance Criteria:

1. Validation and Error Handling:

   • The Group ID should be unique. The system should check for duplicates and prompt the user if a Group ID already exists.
   • The Group Name should be unique within the system. If a user tries to create a group with a name that already exists, the system should notify the user.
   • The Group Allotted Budget should accept only numeric values and validate that it is a positive number. If the input is invalid, the system should display an error message.

2. Successful Creation Feedback:

   • After successful creation, the user should receive a confirmation message indicating that the expense group has been created successfully.
   • The system should display the newly created expense group in the list of expense groups, including all entered details.

3. View and Edit Expense Groups:

   • Users should be able to view a list of all created expense groups with their details.
   • Users should have the option to edit any of the details of an existing expense group, including Group Name, Group Description, and Group Allotted Budget.

4. Delete Expense Groups:

   • Users should have the option to delete an expense group. The system should ask for confirmation before deleting and notify the user once the deletion is successful.