fix(common): make resumption tokens build from request not empty

When creating a resumption token from a request (as done in data provider),
the token is not really empty - the offset is 0. This way, we can still check
for empty tokens (which would be not allowed).

Author: poikilotherm

xoai-common/src/main/java/io/gdcc/xoai/model/oaipmh/ResumptionToken.java

@@ -124,6 +124,7 @@ public Value build() {
         public static ResumptionToken.Value build(Request request) {
             final ResumptionToken.ValueBuilder tokenBuilder = new ResumptionToken.ValueBuilder();
 
+            tokenBuilder.withOffset(0);
             request.getMetadataPrefix().ifPresent(tokenBuilder::withMetadataPrefix);
             request.getFrom().ifPresent(tokenBuilder::withFrom);
             request.getUntil().ifPresent(tokenBuilder::withUntil);