feat: As a user, I want to obtain the previously validated JWT from the context, so that I can use it in my custom plugins with lower priority

[mikyll]

Description

I'd like to extend jwt-auth plugin to save the authenticated JWT in the request context, so that I can easily use it in a plugin which executes after (lower priority), such as a custom ACL. This way I don't have to retrieve it again from the request query parameters, cookies or headers.

Custom plugin example (my-acl.lua):

function _M.rewrite(conf, ctx)
    -- [...]

    local jwt_token = ctx.jwt_obj
    if not jwt_token
    then
        -- Technically this can only happen when the JWT plugin didn't run for this request, or the priority was lower
        core.log.warn("\n\nToken object not found in ctx.\n\n")
        return 401, {message = "Missing JWT token in request"}
    end

    -- [...]
end