purl-next: Collect PURLs for conan C/C++ packages

[pombredanne]

See some base existing code:

• https://github.com/aboutcode-org/purldb/blob/main/minecode/collectors/conan.py
• https://github.com/aboutcode-org/scancode-toolkit/blob/develop/src/packagedcode/conan.py
• https://github.com/aboutcode-org/fetchcode/blob/d125f81a34dda33af8fa8410af869d0696ebcac8/src/fetchcode/package_versions.py#L263

The key data are in a Git repo:

• https://github.com/conan-io/conan-center-index/

See also these conan-related issues:

• Add Fetchcode support for conan fetchcode#176
• Support conan vulnerablecode#1022
• Review and ensure package mined with conan also have non conan purls  #354
• Revisit the multiple download URLs in conandata.yml scancode-toolkit#3654
• collect/ endpoint query for conan PURL with non-existent version returns 'Server Error (500)' #532
• ConanVersionAPI stopped working vulnerablecode#1264

[pombredanne]

Conan is far from great. See:

• ConanVersionAPI stopped working vulnerablecode#1264 (comment)

We could drop it for another well behaved ecosystem if this is too problematic. For now, using the git repo with the index should be good enough.

[pombredanne]

@ziadhany is there a PR for this?

[ziadhany]

@pombredanne Yes, for mine Conan #684, I tested it using the scancode pipeline in https://github.com/ziadhany/conan-test, but it depends on #696, similar to mine Cargo. For on-demand collection, we already have a collector for Conan, but I’m not sure if you mean something else.