feat: implement HoneycombOptions (#2)

## Which problem is this PR solving?

Implements `HoneycombOptions`, including `HoneycombOptions.Builder`, as
per the design doc.

## Short description of the changes

* `Builder` is pre-populated by any XML resource values with the
expected keys.
* There are setters for all values.
* `HoneycombOptions` only contains specific values like
`tracesEndpoint`, whereas the `Builder` has fallback settings like
`setEndpoint`. The specific values are resolved when `build()` is
called.
* Automatic headers and resources are injected upon calling `build()`.
* The only required field is `apiKey`.
* Throws HoneycombException on any fatal configuration error. These
should only be unexpected developer bugs, not expected runtime errors.

## How to verify that this has the expected result

There are comprehensive unit tests that I believe test all XML values,
setters, and fallbacks, as well as any error conditions.

In review please look for the following:
* Are there any missing unit test cases?
* Is the fallback logic correct?
* Are the resources and headers auto-populated correctly?
* Should the error cases actually be error cases?

.gitignore

@@ -7,6 +7,8 @@
 /.idea/workspace.xml
 /.idea/navEditor.xml
 /.idea/assetWizardSettings.xml
+/.idea/androidTestResultsUserPreferences.xml
+/.idea/deploymentTargetSelector.xml
 .DS_Store
 /build
 /captures

build.gradle.kts

@@ -1,6 +1,5 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 plugins {
-    alias(libs.plugins.android.application) apply false
     alias(libs.plugins.jetbrains.kotlin.android) apply false
     alias(libs.plugins.android.library) apply false
-}
+}

core/build.gradle.kts

@@ -10,10 +10,14 @@ android {
     defaultConfig {
         minSdk = 21
 
+        buildConfigField("String","HONEYCOMB_DISTRO_VERSION","\"0.0.1-alpha\"")
+
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
         consumerProguardFiles("consumer-rules.pro")
     }
-
+    buildFeatures {
+        buildConfig = true
+    }
     buildTypes {
         release {
             isMinifyEnabled = false
@@ -24,6 +28,7 @@ android {
         }
     }
     compileOptions {
+        isCoreLibraryDesugaringEnabled = true
         sourceCompatibility = JavaVersion.VERSION_1_8
         targetCompatibility = JavaVersion.VERSION_1_8
     }
@@ -33,11 +38,17 @@ android {
 }
 
 dependencies {
+    // This is required by opentelemetry-android.
+    coreLibraryDesugaring(libs.desugar.jdk.libs)
 
     implementation(libs.androidx.core.ktx)
-    implementation(libs.androidx.appcompat)
-    implementation(libs.material)
+    implementation(libs.opentelemetry.android.agent)
+    implementation(libs.opentelemetry.api)
+    implementation(libs.opentelemetry.sdk)
+    implementation(libs.opentelemetry.exporter.otlp)
+
     testImplementation(libs.junit)
+
     androidTestImplementation(libs.androidx.junit)
     androidTestImplementation(libs.androidx.espresso.core)
-}
+}

core/src/androidTest/java/io/honeycomb/opentelemetry/android/HoneycombOptionsInstrumentedTest.kt

@@ -0,0 +1,81 @@
+package io.honeycomb.opentelemetry.android
+
+import android.os.Build
+import androidx.test.platform.app.InstrumentationRegistry
+import androidx.test.ext.junit.runners.AndroidJUnit4
+
+import org.junit.Test
+import org.junit.runner.RunWith
+
+import org.junit.Assert.*
+import kotlin.time.Duration.Companion.seconds
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ */
+@RunWith(AndroidJUnit4::class)
+class HoneycombOptionsInstrumentedTest {
+    @Test
+    fun builder_usesContext() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        assertEquals("io.honeycomb.opentelemetry.android.test", context.packageName)
+
+        val options = HoneycombOptions.builder(context).build()
+        assertEquals("key", options.tracesApiKey)
+    }
+
+    @Test
+    fun runtimeVersion_isAutomaticallySet() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val options = HoneycombOptions.builder(context).build()
+        assertEquals(
+            mapOf(
+                "service.name" to "unknown_service",
+                "honeycomb.distro.version" to "0.0.1-alpha",
+                "honeycomb.distro.runtime_version" to Build.VERSION.RELEASE,
+            ), options.resourceAttributes
+        )
+    }
+
+    @Test
+    fun source_getString() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val source = HoneycombOptionsResourceSource(context)
+        assertEquals("some string", source.getString("STRING"))
+    }
+
+    @Test
+    fun source_getNullForEmptyString() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val source = HoneycombOptionsResourceSource(context)
+        assertNull(source.getString("EMPTY_STRING"))
+    }
+
+    @Test
+    fun source_getNullForBlankString() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val source = HoneycombOptionsResourceSource(context)
+        assertNull(source.getString("BLANK_STRING"))
+    }
+
+    @Test
+    fun source_getInt() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val source = HoneycombOptionsResourceSource(context)
+        assertEquals(5000, source.getInt("NUMBER"))
+    }
+
+    @Test
+    fun source_getDuration() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val source = HoneycombOptionsResourceSource(context)
+        assertEquals(5.seconds, source.getDuration("NUMBER"))
+    }
+
+    @Test
+    fun source_getBoolean() {
+        val context = InstrumentationRegistry.getInstrumentation().targetContext
+        val source = HoneycombOptionsResourceSource(context)
+        assertEquals(true, source.getBoolean("BOOL"))
+    }
+}

core/src/androidTest/res/values/test_values.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="HONEYCOMB_API_KEY">key</string>
+    <string name="STRING">some string</string>
+    <string name="EMPTY_STRING"></string>
+    <string name="BLANK_STRING">     </string>
+    <integer name="NUMBER">5000</integer>
+    <bool name="BOOL">true</bool>
+</resources>