feat: replace pure SQL strings with SQLair

[kayra1]

Description

This change addresses the final points and closes #84, which modifies the database to have explicit ID's, adds a new status column and associated SQL checks, and utilizes SQLair to simplify database SQL calls.

It also changes the API of the database to fit the new way of using the status column. We now have functions that are abstracted from the direct SQL calls, like UpdateCSR -> AddCertificateToCSR. This is to simplify future development and help avoid getting the database into inconsistent states.

Another change that SQLair brings is the fact that it no longer returns the Result and LastID values that we used to pass along to the HTTP server. This means that successful API calls only receive a JSON message indicating success instead.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that validate the behaviour of the software
• I validated that new and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[gruyaume]

We use the word CSR to mean two different things here, I made a couple of suggestions to decouple CertificateRequest from CSR, where CSR is the X.509 document and a CertificateRequest is a Notary object that contains a CSR, a Certificate and a Status.

[saltiyazan]

In general this looks good.

I added a few minor comments, and I agree with Guillaume that it makes it easier to read if the Request object and the CSR string have different names.

[gruyaume]

The sqlair changes look pretty good! Why include Notary HTTP API changes in this PR though? I don't necessarily disagree with those but they don't match the PR description and unnecessarily complexify the PR, and the review process.

[saltiyazan]

Looks good, given this comment gets resolved.