Completely rewrite and expand documentation for Georm’s core
functionality with detailed explanations, examples, and implementation
details.
Changes:
- Rewrite lib.rs with comprehensive library documentation covering all
features
- Add extensive Georm trait documentation with method-specific details
- Add detailed Defaultable trait documentation with usage patterns
The documentation now provides complete coverage of:
- All CRUD operations with database behavior details
- Composite key support and generated ID structs
- Defaultable field patterns and companion struct generation
- Relationship modeling (field-level and struct-level)
- Error handling and performance characteristics
- PostgreSQL-specific features and optimizations
Introduces support for `#[georm(defaultable)]` attribute on entity
fields. When fields are marked as defaultable, generates companion
`<Entity>Default` structs where defaultable fields become `Option<T>`,
enabling easier entity creation when some fields have database defaults
or are auto-generated.
Key features:
- Generates `<Entity>Default` structs with optional defaultable fields
- Implements `Defaultable<Id, Entity>` trait with async `create` method
- Validates that `Option<T>` fields cannot be marked as defaultable
- Preserves field visibility in generated companion structs
- Only generates companion struct when defaultable fields are present
