[Annotator] DOI HTTP URL saved in place of DOI URI

DOI URIs are not validated when bookmarking a resource and [DOI HTTP URLs can be injected in place of their corresponding DOI URIs](https://hypothes.is/api/search?uri=doi:https://doi.org/10.3998/mp.9460447.0005.205):

```html


```

DOI parsing should handle (incorrect use of) DOI HTTP URLs distinctively from DOI URIs so that only DOI URIs are POST'ed to the API.