Fix StaticMap migrate process plugin doc variable names in examples

Fixed typo in StaticMap boolean documentation. ALTIA linked.

Thank you for your work on this issue. I noticed additional problems that are tightly coupled to this issue and I believe should be solved in conjunction with the current fix.

"foo" and "bar" are both overloaded strings in the Boolean example. I don't like it. This isn't the only place where it occurs in these docs. The default_value example also overloads "bar". It looks like the top/basic example has been copied and pasted several times and the author(s) never realized "foo" and "bar" are already in use. This is inappropriate in general, but especially for a system where the names of data fields are being referenced.

Top/basic example:

 * @code
 * process:
 *   bar:
 *     plugin: static_map
 *     source: foo
 *     map:
 *       from: to
 *       this: that
 *     bypass: TRUE
 * @endcode

We should expand the scope here to remove the overloading of "foo" and "bar" within the individual examples. I suggest that "foo" and "bar" should only be used for the source and destination field names, respectively. Anything else should be changed to alternate metasyntactic variables or something else entirely. For instance in the case of the Boolean example:

 * @code
 * process:
 *   bar:
 *     plugin: static_map
 *     source: foo
 *     map:
 *       0: baz
 *       1: qux
 * @endcode

In that case, the explanatory text already being edited in the MR should be updated with the new values.

Updated MR !16970 to address the review in comment #5.

• Changed the overloaded default_value: bar example to default_value: fallback and updated its explanation.
• Changed the Boolean mapping values to 0: baz and 1: qux and updated the explanation so the field names foo/bar are no longer reused as mapped values.
• The final MR diff contains one documentation file with 6 additions and 6 removals.
• PHP syntax, diff checks, PHPCS, PHPStan, spell-checking, PHP 8.5 unit tests, kernel tests, and functional tests pass.

Pipeline 973264 has unrelated failures in existing PHP 8.6 deprecation tests and the Nightwatch jQuery UI position shim test; retries produced the same failures. This change does not touch those tests or runtime code.

Thank you for making those changes. Let's send it up.

@dcam, thanks for expanding the scope (Comment #5). I completely agree that we should not use the (source and destination) variable names as the values. Personally, I would use something like "vanilla" and "chocolate" as the values, or "blue" and "green", but I will not argue with "alternate metasyntactic variables".

As a nod to my friend Guy Steele, I have to insist on the correct spelling: "quux", not "qux". So I am setting the status back to NW.

From the Wikipedia page on Metasyntactic variables, I see that both are in use. Searching the Drupal codebase, I see that "qux" is used more than "quux". But I am one of the maintainers of the migration subsystem, so I think I can insist on which one to use in the migrate module.

Updated MR !16970 to address the feedback in comment #9. The Boolean mapping example and its accompanying explanation now use `quux` instead of `qux`, as requested. Thank you for the review and clarification.

Updated the change based on the maintainer’s feedback.
The requested quux terminology is now used consistently.
This is ready for review.

Looks good.

I updated the issue title and summary with the expanded scope.

ishfaqafridi85: Thanks for indulging me.

dcam: Thanks for updating the issue summary.

+1 for RTBC

Thanks for improving the documentation!

Committed and pushed to all branches as a documentation improvements are an allowed change,