Attempt to parse any valid information from an oEmbed response
(instead of bailing at the first unexpected data). This should allow
for more partial oEmbed data to be returned, resulting in better /
more URL previews, even if those URL previews are only partial.
By scraping Open Graph information from the HTML even
when an autodiscovery endpoint is found. The results are
then combined to capture as much information as possible
from the page.
* Splits the logic for parsing HTML from the resource handling code.
* Fix a circular import in the oEmbed code (which uses the HTML parsing code).
* Renames some of the HTML parsing methods to:
* Make it clear which methods are "internal" to the module.
* Clarify what the methods do.
* Improved titles (fall back to the author name if there's not title) and include the site name.
* Handle photo/video payloads.
* Include the original URL in the Open Graph response.
* Fix the expiration time (by properly converting from seconds to milliseconds).
The major change is moving the decision of whether to use oEmbed
further up the call-stack. This reverts the _download_url method to
being a "dumb" functionwhich takes a single URL and downloads it
(as it was before #7920).
This also makes more minor refactorings:
* Renames internal variables for clarity.
* Factors out shared code between the HTML and rich oEmbed
previews.
* Fixes tests to preview an oEmbed image.
This adds the format to the request arguments / URL to
ensure that JSON data is returned (which is all that
Synapse supports).
This also adds additional error checking / filtering to the
configuration file to ignore XML-only providers.
