Fix: prevent duplicated encoding request parameters filter

[raccoonback]

Hello.

I found that there is a case where the encoded query parameter in the RewriteRequestParameterGatewayFilterFactory and RemoveRequestHeaderGatewayFilterFactory factory filters encodes the % character again.

For example, if we apply the RemoveRequestHeaderGatewayFilterFactory filter to http://localhost?foo%5B%5D=123&bar=456 to remove the bar parameter, % becomes an encoding target, and the query parameter is duplicated and encoded as http://localhost?foo%255B%255D=123.
I think I should keep the existing encoded query parameter as http://localhost?foo%5B%5D=123.

Therefore, I will explain the items processed for each filter in more detail.

RewriteRequestParameterGatewayFilterFactory

Reason

1. Previously, it checked whether config.getName() existed in ServerWebExchange.getRequest().getQueryParams() and directly replaced config.getReplacement() in UriComponentsBuilder.
   If the query parameter to be replaced is encoded, there is a problem that the name and replacement of config may not be replaced properly.
   Even if we inject it by encoding it in config, it may be encoded twice as a result and it may not be found in ServerWebExchange.getRequest().getQueryParams().
2. Encode not only query parameters but also other segments.
   (since UriComponentsBuilder.build() encodes them by default)
   For example, if it is http://localhost?foo=123#bar=baz%5B%5D, it can be encoded once more up to the fragment, like http://localhost?foo=123#bar=baz%255B%255D.

Solve

1. Modify to replace query parameters based on the return value of ServerWebExchange.getRequest().getQueryParams().
   (ServerWebExchange.getRequest().getQueryParams() internally returns decoded query parameters).

2. Encode only the query parameters and inject them into the UriComponentsBuilder, and do not attempt to encode other segments.

RemoveRequestHeaderGatewayFilterFactory

1. The second reason for RewriteRequestParameterGatewayFilterFactory is the same.
   Modify it to encode only the query parameters segment.

Thanks.