Add an optional description to the payment intent request

service/src/main/java/org/whispersystems/textsecuregcm/configuration/DonationConfiguration.java

@@ -16,6 +16,7 @@ public class DonationConfiguration {
 
   private String uri;
   private String apiKey;
+  private String description;
   private Set<String> supportedCurrencies;
   private CircuitBreakerConfiguration circuitBreaker = new CircuitBreakerConfiguration();
   private RetryConfiguration retry = new RetryConfiguration();
@@ -42,6 +43,16 @@ public class DonationConfiguration {
     this.apiKey = apiKey;
   }
 
+  @JsonProperty
+  public String getDescription() {
+    return description;
+  }
+
+  @VisibleForTesting
+  public void setDescription(final String description) {
+    this.description = description;
+  }
+
   @JsonProperty
   @NotEmpty
   public Set<String> getSupportedCurrencies() {