VPR: Revisit allowing a non-standard landing page (use case: new integrations)

[karenzone]

In #53, I requested the ability to add a non-standard landing page to the Logstash Versioned Plugin Reference. We addressed the immediate need at the time--to support aliased plugins--with #54.

TL;DR from #53 (comment): "The ability to easily add a manual landing page and not have it stomped has broader use cases."

Implementing docs for new plugin integrations might be that use case.

Related:

• [Meta] Doc: Add/update docs for Logstash-to-Logstash communication logstash#15169
• Coordinate a plan for adding new integration docs logstash#15213

[karenzone]

One possible implementation:
I'm picturing a file in which we can enter the name of a new plugin landing page. After the plugin generation runs, it checks this override file. If it found an entry for a manually generated landing page in the override file, it would leave the landing page file alone. This would ensure that we have a VPR landing page to link to for a new integration. and eliminate the manual steps to outsmart the process.

@yaauie indicated in a comment to the original issue, that the overwrite happens here:

docs-tools/versioned_plugins.rb

Lines 205 to 209 in 95137ff

	$stderr.puts("REINDEXING TYPES... #{}\n")
	plugin_names_by_type.each do |type, names|
	$stderr.puts("[type:#{type}] reindexing\n")
	write_type_index(type, names.sort)
	end

When the integration docs are in place and docs are being generated automatically, versioned_plugins.rb could verify that the override entry is not needed, and clear it to remove the cruft.