Support Heptapod (foss.heptapod.net) repositories

[lcarva]

Summary

Add support for resolving and verifying packages hosted on Heptapod (foss.heptapod.net).

Packages

Package	Version	Repository
et-xmlfile	2.0.0	https://foss.heptapod.net/openpyxl/et_xmlfile
openpyxl	3.1.5	https://foss.heptapod.net/openpyxl/openpyxl

Notes

Heptapod is a GitLab-based forge for Mercurial repositories. It exposes a GitLab-compatible API, but the underlying VCS is Mercurial (hg), not git. This may require special handling for cloning and tag resolution.