Issue: SPR-17145

Issue: SPR-16362

This commit allows to specify a custom CorsConfigurationSource
in AbstractHandlerMapping (both Servlet and Reactive variants).

AbstractHandlerMapping#getCorsConfigurations method is now
deprecated.

Issue: SPR-17067

Issue: SPR-17143

Issue: SPR-17141

Issue: SPR-17136

1. Update ExchangeFilterFunctions to delegate internally to
HttpHeaders.setBasicAuth(user, password).

2. Remove deprecation from
ExchangeFilterFunctions.basicAuthentication(String user, String password)
It is still useful as a filter to insert the header.

3. Update deprecation notes.

Issue: SPR-17099

Issue: SPR-17074

Issue: SPR-16933

Issue: SPR-17131

Issue: SPR-17126

Issue: SPR-16398

Issue: SPR-17126

Includes pre-sizing of LinkedHashSet for conversion from array.

Issue: SPR-17123
Issue: SPR-17074

Issue: SPR-15404

Issue: SPR-15404

Issue: SPR-17124

Includes latest dependency updates (Mockito 2.21, Log4J 2.11.1, Hibernate ORM 5.3.4, Protobuf 3.6.1, JRuby 9.2, HtmlUnit 2.32, Selenium 3.14) for Spring Framework 5.1.

Issue: SPR-16388
Issue: SPR-16239

Issue: SPR-17110

Forwarded headers are now processed before ServerWebExchange is created
through ForwardedHeaderTransformer which has the same logic as the
ForwardedHeaderFilter but works on the request only.

ForwardedHeaderFilter is deprecated as of 5.1 but if registered it is
removed from the list of filters and ForwardedHeaderTransformer is used
instead.

Issue: SPR-17072

Issue: SPR-16989

Issue: SPR-17188

Issue: SPR-17117

Issue: SPR-17116

Issue: SPR-17115