[BUG] Search suggestions not working

[frank-ulrich-weber]

Description

Suggester.js uses a POST-Request to send the query parameters,
but within the method process() of class SearchSuggest Sparameters = $request->getQueryParams() is allways empty.
I realised that for a POST-Request (different than for a GET-Request in SearchInDocument class) I
need getParsedBody() insted (my mistake in pull request #1088), but if I do so $parameters is still empty.

If I use a GET-Request within Suggester.js and getQueryParams() in process() (SearchSuggest class) everything is working fine.

Regardless of the fact that the usage of getQueryParams() is wrong in conjunction with a POST-Request,
why does getParsedBody() always deliver an empty string? Does only my test-environment bahave like this?

Reproduction

1. Enable Search Suggestions for at least one existing metadata field
2. Index/Reindex the documents
3. Open the search slot and try

Expected Behavior

Search suggestions should be shown

Screenshots and Examples

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Environment

• OS version: Windwos 10
• RDBMS version: MySQL 5.7
• Apache Solr version: Solr 8.11.4
• TYPO3 version: 11.5.31
• PHP version: 7.4

Additional Context

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