Setup logic to publish the Godot Android library to MavenCentral

[m4gr3d]

This PR follows the instructions from https://getstream.io/blog/publishing-libraries-to-mavencentral-2021/ to setup the logic to publish the Godot Engine Android Library to MavenCentral.

MavenCentral is a repository provided by the Maven community which contains a large number of commonly used libraries.
It's an important tool for java and Android developers as it simplifies the resolution and fetching process for a project's dependencies by build tools like Gradle.

The updated logic will enable to push (automatically) the generated Godot Android Library to MavenCentral so that users can access it by adding a single line to their gradle build file:

dependencies {
    ...
    implementation 'io.github.m4gr3d:godot:<versions>'
    ...
}

Publishing To MavenCentral

• This requires a sonatype account and a GPG key to sign the generated library.
• Provide values for the variables defined in publish-root.gradle. This can either be done via environment variables, or through the local.properties file (that file is not and should not be added to git).
• Generate the Godot Android Library via the usual build process.
• Run the following commands to push the generated library to MavenCentral:
  • cd platform/android/java
  • ./gradlew :lib:publishReleasePublicationToSonatypeRepository
• Follow these steps to review the uploaded binary and release it publicly on MavenCentral.

Notes & TODOs

• I'm using my own sonatype credentials at the moment to publish the library. Eventually, we would want to switch to Godot's own set of credentials.
• Automatic publishing is blocked by above todo. Once we have a set of credentials for Godot, we can automate the publishing of the Godot Android Library by leveraging github workflows as described here.
• Update internal logic (e.g: Android template logic) to leverage the published library via gradle
• Update Android related documentation accordingly.

Part of godotengine/godot-docs#4018
Implements godotengine/godot-proposals#4230

[akien-mga]

Cherry-picked for 3.5.

[akien-mga]

Cherry-picked for 3.4.4.

[hannojg]

@m4gr3d Hey, thanks for providing this! Is the "export" mono-compatible, meaning we can use it for games using mono scripts?

[m4gr3d]

@m4gr3d Hey, thanks for providing this! Is the "export" mono-compatible, meaning we can use it for games using mono scripts?

@hannojg The dependency under io.github.m4gr3d:godot:<versions> is not mono-compatible. Though this is only because the Godot Android library I generate and upload doesn't have mono-enabled.

The sonatype upload script is agnostic, so if a Godot Android library with mono enabled is generated instead, it can be uploaded similarly.

Once we have an official Godot sonatype account (io.github.m4gr3d is my personal account), it makes sense to include the mono library as part of the offered dependencies.

cc @akien-mga