Pending acquire queue has reached its maximum size

[Luboš Račanský]

When maxIdleTime is specified, we start seeing this error:

org.springframework.web.reactive.function.client.WebClientRequestException: Pending acquire queue has reached its maximum size of 32
	at org.springframework.web.reactive.function.client.ExchangeFunctions$DefaultExchangeFunction.lambda$wrapException$9(ExchangeFunctions.java:136)
	Suppressed: The stacktrace has been enhanced by Reactor, refer to additional information below: 
Error has been observed at the following site(s):
	*__checkpoint ⇢ Request to POST http://localhost:8080/powerauth-java-server/rest/v3/token/validate [DefaultWebClient]
Original Stack Trace:

Logic behind return HttpClient.create(ConnectionProvider.builder("custom").build()); uses different values than HttpClient.create().
See reactor/reactor-netty#2052 (comment)

A follow-up to #187