RequestSignatureInterceptor signs decoded path instead of raw path, causing 400 for any request whose URI contains percent-encoded characters (regression since the HttpClient 5 migration)

[ykatola]

Since the migration to Apache HttpClient 5 (v17.x onwards, still present in
18.0.3), ApacheHttpRequestToSign#getPath() returns the decoded request
path while the request is sent over the wire with the encoded path. This
causes a canonical-string mismatch between client and server for every request
whose URI contains characters that get percent-encoded (spaces, /, +, %,
non-ASCII letters such as Æ/Ø/Å/é, …). The Digipost server rejects the
signature with HTTP 400, and because the rejected response is unsigned, the
client-side ResponseSignatureInterceptor additionally logs
Missing X-Digipost-Signature header.

In v16.4.1 (HttpClient 4) the same method used URI#getRawPath() and the bug
did not exist.