[FLORA-61] Start the data model for security advisories

[tchoutri]

Proposed changes

This PR introduces the initial data model for security advisories.

The database components are as follow:

• security_advisories, which encode most of the metadata, and to where affected packages refer
• affected_packages represent the packages affected by an advisory, pointing to the advisory. Affected packages have one or multiple affected version ranges associated.
• affected_version_ranges represent a link between an affected package, and the releases where the vulnerability is introduced and fixed.

Linked

• https://github.com/haskell/security-advisories/pull/241

Contributor checklist

• [x] My PR is related to #554
• [x] I have read and understood the CONTRIBUTING guide
• [x] I have inserted my change and a link to this PR in the CHANGELOG
• [ ] I have updated documentation in ./docs/docs if a public feature has a behaviour change

[tchoutri]

@MangoIV The standalone syntax for NFData does not work if the type does not implement Generic

[MangoIV]

if the type does not implement Generic

I mistook that for granted.

[tchoutri]

@tristanCacqueray @blackheaven @frasertweedale Please let me know what you think of this. For the moment I'm filing advisories of the GHC components (haddock included) in the ghc package.

[tchoutri]

@MangoIV yes, the propagation of the information is the next PR, I just wanted to focus on the data model here. :)