Implement restrictive deserialization

Following the API guidelines, we're implementing a restrictive
deserialization strategy https://opensource.zalando.com/restful-api-guidelines/#109

src/main/java/org/zalando/nakadi/config/JsonConfig.java

@@ -79,7 +79,7 @@ public Enum deserialize(final JsonParser jp, final DeserializationContext ctxt)
 
             try {
                 if (rawClass.equals(Audience.class)) {
-                    return Audience.valueOf(jpValueAsString.toUpperCase().replaceAll("-", "_"));
+                    return Audience.fromString(jpValueAsString);
                 } else {
                     return Enum.valueOf(rawClass, jpValueAsString.toUpperCase());
                 }
@@ -109,7 +109,7 @@ private static class LowerCaseEnumJsonSerializer extends StdSerializer<Enum> {
         public void serialize(final Enum value, final JsonGenerator jgen, final SerializerProvider provider)
                 throws IOException {
             if (value.getClass().equals(Audience.class)) {
-                jgen.writeString(value.name().toLowerCase().replaceAll("_", "-"));
+                jgen.writeString(((Audience)value).getText());
             } else {
                 jgen.writeString(value.name().toLowerCase());
             }

src/main/java/org/zalando/nakadi/domain/Audience.java

@@ -1,5 +1,28 @@
 package org.zalando.nakadi.domain;
 
 public enum Audience {
-    COMPONENT_INTERNAL, BUSINESS_UNIT_INTERNAL, COMPANY_INTERNAL, EXTERNAL_PARTNER, EXTERNAL_PUBLIC
+    COMPONENT_INTERNAL("component-internal"),
+    BUSINESS_UNIT_INTERNAL("business-unit-internal"),
+    COMPANY_INTERNAL("company-internal"),
+    EXTERNAL_PARTNER("external-partner"),
+    EXTERNAL_PUBLIC("external-public");
+
+    private String text;
+
+    Audience(final String text) {
+        this.text = text;
+    }
+
+    public String getText() {
+        return this.text;
+    }
+
+    public static Audience fromString(final String text) {
+        for (final Audience audience : Audience.values()) {
+            if (audience.text.equals(text)) {
+                return audience;
+            }
+        }
+        throw new IllegalArgumentException();
+    }
 }