* [fix] engine: pinterest - fix empty titles and complete modernization
The titles from the fields ``title`` and ``grid_title`` are mostly empty or have
short strings without meaningful content. Various fields for the title are now
being queried, which have more informative value.
As part of the bug fix, the engine was completely revised and modernized.
Related:
- https://github.com/searxng/searxng/pull/6690#issuecomment-5631113121
Co-authored-by: @vojkovic
- apparently the API now requires a `X-Pinterest-PWS-Handler` in order to
properly function (extracted from their web UI)
- the other `X-Pinterest` headers here are added in case they become mandatory
too
Closes: https://github.com/searxng/searxng/issues/4812
