Add isInDebug variable to simulate debug/release configs for tests (#2566)

* `isInDebug` as `ThreadLocal<Boolean>`

* Use a simple var for `isInDebug` and add a helper method to test release mode, when running the debug test.

* Add some more docs

---------

Co-authored-by: Benoit Marty <benoit@matrix.org>

libraries/androidutils/src/main/kotlin/io/element/android/libraries/androidutils/metadata/IsInDebug.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2024 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.androidutils.metadata
+
+import io.element.android.libraries.androidutils.BuildConfig
+
+/**
+ * true if the app is built in debug mode.
+ * For testing purpose, this can be changed with [withReleaseBehavior].
+ */
+var isInDebug: Boolean = BuildConfig.DEBUG
+    private set
+
+/**
+ * Run the lambda simulating the app is in release mode.
+ *
+ * **IMPORTANT**: this should **ONLY** be used for testing purposes.
+ */
+fun withReleaseBehavior(lambda: () -> Unit) {
+    isInDebug = false
+    lambda()
+    isInDebug = BuildConfig.DEBUG
+}