Properly batch contact inserts.

Fixes #8580

test/unitTest/java/org/thoughtcrime/securesms/util/UtilTest.java

@@ -0,0 +1,52 @@
+package org.thoughtcrime.securesms.util;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class UtilTest {
+
+  @Test
+  public void chunk_oneChunk() {
+    List<String> input = Arrays.asList("A", "B", "C");
+
+    List<List<String>> output = Util.chunk(input, 3);
+    assertEquals(1, output.size());
+    assertEquals(input, output.get(0));
+
+    output = Util.chunk(input, 4);
+    assertEquals(1, output.size());
+    assertEquals(input, output.get(0));
+
+    output = Util.chunk(input, 100);
+    assertEquals(1, output.size());
+    assertEquals(input, output.get(0));
+  }
+
+  @Test
+  public void chunk_multipleChunks() {
+    List<String> input = Arrays.asList("A", "B", "C", "D", "E");
+
+    List<List<String>> output = Util.chunk(input, 4);
+    assertEquals(2, output.size());
+    assertEquals(Arrays.asList("A", "B", "C", "D"), output.get(0));
+    assertEquals(Arrays.asList("E"), output.get(1));
+
+    output = Util.chunk(input, 2);
+    assertEquals(3, output.size());
+    assertEquals(Arrays.asList("A", "B"), output.get(0));
+    assertEquals(Arrays.asList("C", "D"), output.get(1));
+    assertEquals(Arrays.asList("E"), output.get(2));
+
+    output = Util.chunk(input, 1);
+    assertEquals(5, output.size());
+    assertEquals(Arrays.asList("A"), output.get(0));
+    assertEquals(Arrays.asList("B"), output.get(1));
+    assertEquals(Arrays.asList("C"), output.get(2));
+    assertEquals(Arrays.asList("D"), output.get(3));
+    assertEquals(Arrays.asList("E"), output.get(4));
+  }
+}