Create utility endpoint for currency conversion

service/src/main/java/org/whispersystems/textsecuregcm/entities/CurrencyConversionEntity.java

@@ -0,0 +1,30 @@
+package org.whispersystems.textsecuregcm.entities;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.Map;
+
+public class CurrencyConversionEntity {
+
+  @JsonProperty
+  private String base;
+
+  @JsonProperty
+  private Map<String, Double> conversions;
+
+  public CurrencyConversionEntity(String base, Map<String, Double> conversions) {
+    this.base        = base;
+    this.conversions = conversions;
+  }
+
+  public CurrencyConversionEntity() {}
+
+  public String getBase() {
+    return base;
+  }
+
+  public Map<String, Double> getConversions() {
+    return conversions;
+  }
+
+}

service/src/main/java/org/whispersystems/textsecuregcm/entities/CurrencyConversionEntityList.java

@@ -0,0 +1,29 @@
+package org.whispersystems.textsecuregcm.entities;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import java.util.List;
+
+public class CurrencyConversionEntityList {
+
+  @JsonProperty
+  private List<CurrencyConversionEntity> currencies;
+
+  @JsonProperty
+  private long timestamp;
+
+  public CurrencyConversionEntityList(List<CurrencyConversionEntity> currencies, long timestamp) {
+    this.currencies = currencies;
+    this.timestamp  = timestamp;
+  }
+
+  public CurrencyConversionEntityList() {}
+
+  public List<CurrencyConversionEntity> getCurrencies() {
+    return currencies;
+  }
+
+  public long getTimestamp() {
+    return timestamp;
+  }
+}