Add new CSAF validation rules and optimize test structure (#38)

* Add new CSAF validation rules and optimize test structure

Introduced additional validation rules (6.1.37 - 6.1.42) for CSAF 2.1, including checks for sharing group names, TLP consistency, and PURLs. Refactored test structure to use a centralized helper function for streamlined testing and reduced redundancy.

* Enhance datetime validation with chrono-based parsing checks

Added a chrono-based plausibility check to ensure RFC3339 date-time strings are valid beyond regex matching. This improvement catches invalid cases like out-of-range dates, providing more accurate validation error messages.

* Refactor product tree traversal and validation logic

Introduced a unified product tree traversal API via `visit_all_products` and `visit_branches_rec`, simplifying branch recursion and validation. Replaced specific `gather_product_definitions` and custom traversal functions with reusable logic, ensuring consistency and reducing code duplication. Additionally, improved modularity by renaming traits and refining parameterized implementations for better clarity.

Author: milux

Cargo.lock

@@ -9,6 +9,8 @@ serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 chrono = { version = "0.4", features = ["serde"] }
 regex = "1"
+glob = "0.3.2"
+purl = "0.1"
 
 [build-dependencies]
 schemars = "0.8"