Implemented Data Model Entities

[sreedatthap]

This pull request includes the implementation of the data model entities for the application. The following changes were made:

• Created entity classes for each entity in the data model.
• Each entity is annotated with @entity, and the id field is auto-generated.
• Added constructors for entity initialization and getter/setter methods for instance variables.
• Configured necessary @column annotations to ensure correct mapping to the database.
• Followed the project guidelines for entity creation and ensured proper structure.

These changes prepare the application to handle database operations with the newly defined entities.