public Builder vespaVersion(String vespaVersion) {
            Optional<Version> version = Optional.empty();
            if (vespaVersion != null && !vespaVersion.isEmpty()) {
                version = Optional.of(Version.fromString(vespaVersion));
            }
            this.vespaVersion = version;
            return this;
        }
Parameters for preparing an application. Immutable.

@author Ulf Lilleengen
configserver/src/main/java/com/yahoo/vespa/config/server/session/PrepareParams.java