We catch MaskedObjectException at the webapp level and display a
specific error page. The page lists the opaque identifier of the masking
requests and the legal email address where to send inquiries.

We also add support for MaskedObjectException in API responses.

Thanks to @anlambert for deduplicating the error templates and fixtures.
Thanks to @vlorentz for improving the wording of the error page.

That make it possible to show the end user the exception for the failure
of the loading task, if any.

Related to #4805

Add /provenance/whereis/ Web API endpoint wrapping call to whereis
operation from swh-provenance API. It enables to get a qualified SWHID
with provenance info from a core SWHID.

Add /provenance/whereare/ Web API endpoint wrapping call to whereare
operation from swh-provenance API. It enables to get qualified SWHIDs
with provenance info from a list of core SWHIDs.

These endpoints are protected by authentication and a user permission
named "swh.web.api.provenance".

Related to swh/infra/sysadm-environment#5397.

It enables to simplify the declaration of a webapp URL containing
a SWHID in its path.

Previously, it was hard to display the most recent counter value in
histogram tooltip. This is no longer the case with this change.

Add Web API endpoint /api/1/origin/save/bulk/requests/ enabling a user
to list the save bulk requests he submitted and get info URLs about them.

Related to #4802.

showdown-highlight is a plugin for showdownjs enabling to highlight a code
block with highlightjs when rendering markdown to html.

There was some issues at the time to use the npm version but it is no longer
the case so fetch that code from the npm registry instead of vendoring it
in swh-web frontend code.

That updated version also fixes some rendering issues related to code blocks
with no explicitly declared programming language.

Add Web API endpoint /origin/save/bulk/request/(request_id)/ to get
feedback about a previously sent save bulk request.

The endpoint requires authentication and special permission to be
queried, also only the user that submitted the request or SWH staff
members can query it.

It returns for each submitted origin the following info:

- the origin URL
- the visit type
- the origin status regarding its processing by the bulk save lister,
  either pending, accepted or rejected
- the last scheduling date if any
- the last visit date if any
- the last visit status if any
- the last snapshot SWHID if any
- the rejection reason if the origin was rejected by the lister
- the browse URL if the origin was successfully visited

These info are returned in a paginated way as the number of submitted
origins can be large.

Related to #4802.

Allow to define endpoint route using a simple string instead of a
regular expression.

It notably enables to use django parameter type annotations like
int or uuid.

test_get_snapshot_context_with_origin sometimes fails due to
a date comparison issue (seconds might be offset by 1).

This command will copy all the active mailmaps in the masking proxy DB
which dsn is given as argument.

It is similar to the (now deprecated) sync_mailmaps command, but since
it does not modify the Person table of the storage any more, it does not
need the timestamp-based detection to determine which entries are to be
enabled or disabled; it simply rewrite the whole displayname table
every time it's called, if need be.

A '--force' option allows to enforce rewrite the whole table even if no
update has been detected in the displayname database.

Extract tests for (soon to be legacy) sync_mailmap related fatures in a
dedicated test file.

If not provided, .get() would return None, which makes get_save_origin_requests_to_update
return every SCN request. There is no reason to want the webhook to do that.

When a user request the cooking of a bundle not referenced in the
browser local storage and that bundle has already been cooked but
no longer available in vault cache, ensure the recooking request
is sent as previously that edge case was not handled.

Related to #4804.

test_snapshot_browse_with_id_origin_and_timestamp is flaky due to
a date comparison issue (seconds might be offset by 1) so mark it
as such with pytest.

Apply suggestion from rboyer.

Add javascript function based on the use of the anchorjs package enabling
to add anchors to headings. It enables users to easily get links to parts
of a page by hovering mouse cursor on page headings.

Use it in homepage, api pages but also in pages rendering a README file
from the archive.