It’s good to see that the ic-certification library is bringing you in the right direction.
In case you’re interested, some other canisters serving custom http_request endpoints instead of an asset canister on custom domains include Internet Identity, NNS Dapp, Juno, and Taggr. However, they are all implemented in Rust rather than Motoko, but the code may still be helpful.
I agree the documentation is lacking in this department. It’s something that I intend to work on in the coming months. My focus will initially be on the Rust side, but Motoko will come later if the community doesn’t pick up BNT-13 in the meantime.