Unescaped "@" in ContextProviderInterface doc comment

Problem/Motivation

API page: https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Plugin%21...

Enter a descriptive title (above) relating to interface ContextProviderInterface, then describe the problem you have found:

The documentation block in code looks like this:

/**
 * Defines an interface for providing plugin contexts.
 *
 * Implementations only need to deal with unqualified context IDs so they only
 * need to be unique in the context of a given service provider.
 *
 * The fully qualified context ID then includes the service ID:
 * @{service_id}:{unqualified_context_id}.
 *
 * @see \Drupal\Core\Plugin\Context\ContextRepositoryInterface
 */

But in the API page this shows up mangled, because the "@{service_id}" is interpreted as a doxygen tag. It ends up looking like this:
The fully qualified context ID then includes the service ID: service_id}:{unqualified_context_id}.
While it should read:
The fully qualified context ID then includes the service ID: @{service_id}:{unqualified_context_id}.

Proposed resolution

There are two viable patches posted here:

1. #3014969-2: Unescaped "@" in ContextProviderInterface doc comment escapes the @ - this is the same method as used elsewhere in core, see #213120: Escape \@.
2. #3014969-4: Unescaped "@" in ContextProviderInterface doc comment puts the problem text in a @code/@endcode block.

Remaining tasks

None

User interface changes

None

API changes

None

Data model changes

None

Release notes snippet

None