Fix tab escape in character gropu and add tests

Author: alexander-alderman-webb

sentry/src/main/java/io/sentry/SentryTraceHeader.java

@@ -18,7 +18,7 @@ public final class SentryTraceHeader {
   // Use numbered capture groups for Android API level < 26 compatibility
   private static final Pattern SENTRY_TRACEPARENT_HEADER_REGEX =
       Pattern.compile(
-          "^[ \\t]*([0-9a-f]{32})-([0-9a-f]{16})(-[01])?[ \\t]*$", Pattern.CASE_INSENSITIVE);
+          "^[ \t]*([0-9a-f]{32})-([0-9a-f]{16})(-[01])?[ \t]*$", Pattern.CASE_INSENSITIVE);
 
   public SentryTraceHeader(
       final @NotNull SentryId traceId,

sentry/src/test/java/io/sentry/SentryTraceHeaderTest.kt

@@ -132,6 +132,26 @@ class SentryTraceHeaderTest {
     assertNull(header.isSampled)
   }
 
+  @Test
+  fun `handles header without sampling decision and leading whitespace`() {
+    val sentryId = SentryId()
+    val spanId = SpanId()
+    val header = SentryTraceHeader(" \t $sentryId-$spanId")
+    assertEquals(sentryId, header.traceId)
+    assertEquals(spanId, header.spanId)
+    assertNull(header.isSampled)
+  }
+
+  @Test
+  fun `handles header without sampling decision and trailing whitespace`() {
+    val sentryId = SentryId()
+    val spanId = SpanId()
+    val header = SentryTraceHeader("$sentryId-$spanId \t ")
+    assertEquals(sentryId, header.traceId)
+    assertEquals(spanId, header.spanId)
+    assertNull(header.isSampled)
+  }
+
   @Test
   fun `when sampling decision is not made, getValue returns header with traceId and spanId`() {
     val sentryId = SentryId()