LCFS - Update Table and Column Descriptions in SQLAlchemy Models

**Description:** Our database schema, defined in SQLAlchemy models, lacks descriptive comments for tables and columns. This task is to update our models with clear, informative comments for each table and column, detailing their purposes, data types, and any special considerations. This enhancement aims to improve the understanding of our data model for developers and external database architects, facilitating easier navigation and comprehension.

**Purpose:** To improve documentation within the codebase, ensuring that the database schema is well-understood, which will aid in maintenance, development, and external consultation.

**Acceptance Criteria:**
- [ ] Add descriptive comments to all tables in the SQLAlchemy models, outlining their roles and usage.
- [ ] Update each column with comments that describe its purpose, data type, and constraints or relationships.
- [ ] Ensure all comments are clear, concise, and accurate.
- [ ] Documentation guidelines for maintaining table and column comments are updated or created.

**Additional context:**
- Coordinate with team members for insights on table and column functionalities.
- Adopt a standardized format for comments to ensure consistency across the schema.

Locate the SQLAlchemy model definitions and inventory every table and column that needs a comment. Review any existing documentation guidelines and consult team members about unclear schema roles or relationships. Done means all tables and columns have clear, consistent comments and the guidelines for maintaining them are updated or created.

Written by the indexing model from the issue text.