Add an experiment enrollment manager.

service/src/main/java/org/whispersystems/textsecuregcm/configuration/dynamic/DynamicConfiguration.java

@@ -1,5 +1,19 @@
 package org.whispersystems.textsecuregcm.configuration.dynamic;
 
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import javax.validation.Valid;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Optional;
+
 public class DynamicConfiguration {
 
+  @JsonProperty
+  @Valid
+  private Map<String, DynamicExperimentEnrollmentConfiguration> experiments = Collections.emptyMap();
+
+  public Optional<DynamicExperimentEnrollmentConfiguration> getExperimentEnrollmentConfiguration(final String experimentName) {
+    return Optional.ofNullable(experiments.get(experimentName));
+  }
 }

service/src/main/java/org/whispersystems/textsecuregcm/configuration/dynamic/DynamicExperimentEnrollmentConfiguration.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2021 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.configuration.dynamic;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+import javax.validation.Valid;
+import javax.validation.constraints.Max;
+import javax.validation.constraints.Min;
+import java.util.Collections;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+public class DynamicExperimentEnrollmentConfiguration {
+
+    @JsonProperty
+    @Valid
+    private Set<UUID> enrolledUuids = Collections.emptySet();
+
+    @JsonProperty
+    @Valid
+    @Min(0)
+    @Max(100)
+    private int enrollmentPercentage = 0;
+
+    public Set<UUID> getEnrolledUuids() {
+        return enrolledUuids;
+    }
+
+    public int getEnrollmentPercentage() {
+        return enrollmentPercentage;
+    }
+}