Fedora 35 support was dropped, so we can update to a newer Go.
Stable RHEL 8 and 9 and Fedora 36 ships Go 1.18, so let's switch to it.
"//go:build" directives are now apparently enforced by go fmt, so that's why
there were added.
Also, all the github actions were adjusted to use Go 1.18.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
Write an openapi spec for the worker API and use `deepmap/oapi-codegen`
to generate scaffolding for the server-side using the `labstack/echo`
server.
Incidentally, echo by default returns the errors in the same format that
worker API always has:
{ "message": "..." }
The API itself is unchanged to make this change easier to understand. It
will be changed to better suit our needs in future commits.
