Improve logging, format timestamp and show app build infos (DEV) (#1719)

* Log current build and verison information.

* Print formatted date instead of EPOCH millis.

* Use correct instant (joda time).

Co-authored-by: Ralf Gehrer <ralfgehrer@users.noreply.github.com>

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/CWADebug.kt

@@ -17,6 +17,9 @@ object CWADebug {
         if (isDeviceForTestersBuild) {
             fileLogger = FileLogger(application)
         }
+
+        Timber.i("CWA version: %s (%s)", BuildConfig.VERSION_CODE, BuildConfig.GIT_COMMIT_SHORT_HASH)
+        Timber.i("CWA flavor: %s (%s)", BuildConfig.FLAVOR, BuildConfig.BUILD_TYPE)
     }
 
     val isDebugBuildOrMode: Boolean

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/debug/FileLoggerTree.kt

@@ -2,6 +2,7 @@ package de.rki.coronawarnapp.util.debug
 
 import android.annotation.SuppressLint
 import android.util.Log
+import org.joda.time.Instant
 import timber.log.Timber
 import java.io.File
 import java.io.FileOutputStream
@@ -55,7 +56,7 @@ class FileLoggerTree(private val logFile: File) : Timber.DebugTree() {
     override fun log(priority: Int, tag: String?, message: String, t: Throwable?) {
         logWriter?.let {
             try {
-                it.write("${System.currentTimeMillis()}  ${priorityToString(priority)}/$tag: $message\n")
+                it.write("${Instant.now()}  ${priorityToString(priority)}/$tag: $message\n")
                 it.flush()
             } catch (e: IOException) {
                 Timber.tag(TAG).e(e)