Bump retrofit from 2.4.0 to 2.9.0

[dependabot]

Bumps retrofit from 2.4.0 to 2.9.0.

Changelog

Sourced from retrofit's changelog.

Version 2.9.0 (2020-05-20)

• New: RxJava 3 adapter!

  The Maven coordinates are com.squareup.retrofit2:adapter-rxjava3.

  Unlike the RxJava 1 and RxJava 2 adapters, the RxJava 3 adapter's create() method will produce asynchronous HTTP requests by default. For synchronous requests use createSynchronous() and for synchronous on a scheduler use createWithScheduler(..).

Version 2.8.2 (2020-05-18)

• Fix: Detect running on the Android platform by using system property rather than the presence of classes. This ensures that even when you're running on the JVM with Android classes present on the classpath you get JVM semantics.
• Fix: Update to OkHttp 3.14.9 which contains an associated Android platform detection fix.

Version 2.8.1 (2020-03-25)

• Fix: Do not access MethodHandles.Lookup on Android API 24 and 25. The class is only available on Android API 26 and higher.

Version 2.8.0 (2020-03-23)

• New: Add Call.timeout() which returns the okio.Timeout of the full call.
• Fix: Change Call.awaitResponse() to accept a nullable response type.
• Fix: Support default methods on Java 14+. We had been working around a bug in earlier versions of Java. That bug was fixed in Java 14, and the fix broke our workaround.

Version 2.7.2 (2020-02-24)

• Fix: Update to OkHttp 3.14.7 for compatibility with Android R (API 30).

Version 2.7.1 (2020-01-02)

• Fix: Support 'suspend' functions in services interfaces when using 'retrofit-mock' artifact.

Version 2.7.0 (2019-12-09)

... (truncated)

Commits

• bd33a5d Prepare version 2.9.0
• 762f590 Add releasing steps
• 8796695 Merge pull request #3374 from ctlove0523/master
• 467764b Update Maven references to Gradle
• ab1d46d Merge pull request #3315 from mickverm/rxjava3-adapter
• f68ceb4 Added RxJava3 adapter
• 1078fd1 Prepare next development version
• 16205e9 Add pom descriptions for each deployed artifact
• 9710e64 Prepare version 2.8.2
• 8e38431 Merge pull request #3394 from square/jw/okhttp/2020-05-17
• Additional commits viewable in compare view

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