Sentry

* `pubspec.yaml` and example code clean-up.

Java + Android

This release marks the re-unification of Java and Android SDK code bases.
It's based on the Android 2.0 SDK, which implements [Sentry's unified API](https://develop.sentry.dev/sdk/unified-api/).

Considerable changes were done, which include a lot of improvements. More are covered below, but the highlights are:

- Improved `log4j2` integration
- Capture breadcrumbs for level INFO and higher
- Raises event for ERROR and higher.
- Minimum levels are configurable.
- Optionally initializes the SDK via appender.xml
- Dropped support to `log4j`.
- Improved `logback` integration
- Capture breadcrumbs for level INFO and higher
- Raises event for ERROR and higher.
- Minimum levels are configurable.
- Optionally initializes the SDK via appender.xml
- Configurable via Spring integration if both are enabled
- Spring
- No more duplicate events with Spring and logback
- Auto initalizes if DSN is available
- Configuration options available with auto complete
- Google App Engine support dropped

What’s Changed

- Callback to validate SSL certificate ([944](https://github.com/getsentry/sentry-java/pull/944))
- Attach stack traces enabled by default

Android specific

- Release health enabled by default for Android
- Sync of Scopes for Java -> Native (NDK)
- Bump Sentry-Native v0.4.2
- Android 11 Support

[Android migration docs](https://docs.sentry.io/platforms/android/migration/#migrating-from-sentry-android-2x-to-sentry-android-3x)

Java specific

- Unified API for Java SDK and integrations (Spring, Spring boot starter, Servlet, Logback, Log4j2)

New Java [docs](https://docs.sentry.io/platforms/java/) are live and being improved.

Acquisition

Packages were released on [`bintray sentry-java`](https://dl.bintray.com/getsentry/sentry-java/io/sentry/), [`bintray sentry-android`](https://dl.bintray.com/getsentry/sentry-android/io/sentry/), [`jcenter`](https://jcenter.bintray.com/io/sentry/) and [`mavenCentral`](https://repo.maven.apache.org/maven2/io/sentry/)

Where is the Java 1.7 code base?

The previous Java releases, are all available in this repository through the tagged releases.

- feat: Adds `ElectronOfflineNetTransport` and makes it the default transport
- feat: Adds `AdditionalContext` integration that includes additional device and enables it by default (390)
- feat: Renames `ElectronEvents ` to `ElectronBreadcrumbs` and allows more complex configuration
- fix: Fixes bundling of preload code (396)
- feat: Adds breadcrumbs and tracing for the Electron `net` module (395)
- feat: Breadcrumbs and events for child processes (398)
- feat: Capture minidumps for GPU crashes with `SentryMinidump` integration (398)

- fix: Enable CORS for custom protocol

- fix: Correctly handle previously crashed/abnormal sessions (379)
- feat: Remove the need for preload script in most cases by falling back to custom protocol (377)
- fix: Fix issues with incorrect environment (378)
- test: Refactor tests and examples into self contained apps (373)
- fix: Fixed a number of issues with incorrect context (373)

**Tracing API**

In this version we released API for Tracing. `\Sentry\startTransaction` is your entry point for manual instrumentation.
More information can be found in our [Performance](https://docs.sentry.io/product/performance/) docs or specific
[PHP SDK](https://docs.sentry.io/platforms/php/) docs.

**Breaking Change**: This version uses the [envelope endpoint](https://develop.sentry.dev/sdk/envelopes/). If you are
using an on-premise installation it requires Sentry version `>= v20.6.0` to work. If you are using
[sentry.io](https://sentry.io) nothing will change and no action is needed.

- [BC BREAK] Remove the deprecated code that made the `Hub` class a singleton (1038)
- [BC BREAK] Remove deprecated code that permitted to register the error, fatal error and exception handlers at once (1037)
- [BC BREAK] Change the default value for the `error_types` option from `E_ALL` to the value get from `error_reporting()` (1037)
- [BC BREAK] Remove deprecated code to return the event ID as a `string` rather than an object instance from the transport, the client and the hub (1036)
- [BC BREAK] Remove some deprecated methods from the `Options` class. (1047)
- [BC BREAK] Remove the deprecated code from the `ModulesIntegration` integration (1047)
- [BC BREAK] Remove the deprecated code from the `RequestIntegration` integration (1047)
- [BC BREAK] Remove the deprecated code from the `Breadcrumb` class (1047)
- [BC BREAK] Remove the deprecated methods from the `ClientBuilderInterface` interface and its implementations (1047)
- [BC BREAK] The `Scope::setUser()` method now always merges the given data with the existing one instead of replacing it as a whole (1047)
- [BC BREAK] Remove the `Context::CONTEXT_USER`, `Context::CONTEXT_RUNTIME`, `Context::CONTEXT_TAGS`, `Context::CONTEXT_EXTRA`, `Context::CONTEXT_SERVER_OS` constants (1047)
- [BC BREAK] Use PSR-17 factories in place of the Httplug's ones and return a promise from the transport (1066)
- [BC BREAK] The Monolog handler does not set anymore tags and extras on the event object (1068)
- [BC BREAK] Remove the `UserContext`, `ExtraContext` and `Context` classes and refactor the `ServerOsContext` and `RuntimeContext` classes (1071)
- [BC BREAK] Remove the `FlushableClientInterface` and the `ClosableTransportInterface` interfaces (1079)
- [BC BREAK] Remove the `SpoolTransport` transport and all its related classes (1080)
- Add the `EnvironmentIntegration` integration to gather data for the `os` and `runtime` contexts (1071)
- Refactor how the event data gets serialized to JSON (1077)


Changelog