Add GraalVM Native Image support

[realbucksavage]

Attempting to build a native image (./gradlew clean dockerbuildnative) results in this error:

Error: com.oracle.svm.hosted.substitute.DeletedElementException: Unsupported type java.util.JapaneseImperialCalendar is reachable
To diagnose the issue, you can add the option --report-unsupported-elements-at-runtime. The unsupported element is then reported at run time when it is accessed the first time.
Detailed message:
Trace:
        at parsing java.util.Calendar$Builder.build(Calendar.java:1508)
Call path from entry point to java.util.Calendar$Builder.build():
        at java.util.Calendar$Builder.build(Calendar.java:1473)
        at io.swagger.v3.parser.util.OpenAPIDeserializer.toDate(OpenAPIDeserializer.java:2624)
        at io.swagger.v3.parser.util.OpenAPIDeserializer.getDecodedObject(OpenAPIDeserializer.java:2572)
        at io.swagger.v3.parser.util.OpenAPIDeserializer.getSchema(OpenAPIDeserializer.java:2383)
        at io.swagger.v3.parser.ResolverCache.loadRef(ResolverCache.java:159)
        at io.swagger.v3.parser.processors.ExternalRefProcessor.processRefToExternalSchema(ExternalRefProcessor.java:89)
        at io.swagger.v3.parser.processors.ExternalRefProcessor.processRefSchemaObject(ExternalRefProcessor.java:893)
        at io.swagger.v3.parser.processors.ExternalRefProcessor.lambda$processRefToExternalPathItem$1(ExternalRefProcessor.java:339)
        at io.swagger.v3.parser.processors.ExternalRefProcessor$$Lambda$2388/0x00000007c1fb2840.accept(Unknown Source)
        at java.util.Optional.ifPresent(Optional.java:183)
        at java.lang.Runtime$Version.toString(Runtime.java:1392)
        at java.lang.String.valueOf(String.java:2951)
        at java.lang.StringBuilder.append(StringBuilder.java:168)
        at java.net.Proxy.<init>(Proxy.java:95)
        at com.oracle.svm.jni.JNIJavaCallWrappers.jniInvoke_VARARGS_Proxy_constructor_4c292c8081165fc77e6ffffc00ffc9c7f9d770eb(generated:0)