Add code samples for Remote Config operations

[lahirumaramba]

• Related to: fix: Cleaning up FirebaseApp state management firebase-admin-java#476

• Samples to appear on https://firebase.google.com/docs/remote-config/automate-rc and https://firebase.google.com/docs/remote-config/templates

[samtstern]

@lahirumaramba LGTM, I assume the CI failures are because the SDK has not released yet? Please wait until CI is green to merge these.

[kroikie]

LGTM

[lahirumaramba]

@lahirumaramba LGTM, I assume the CI failures are because the SDK has not released yet? Please wait until CI is green to merge these.

@samtstern Thanks! Yes, the current SDK the project is pointing to does not have the new RC features, hence the CI failures. Once the SDK is released, do you think I should update admin/build.gradle as well? If so, I could include that change in the same PR.

[samtstern]

@lahirumaramba yep exactly, if you bump the dependency in this PR as well then it will be green before you merge.

If these snippets have to appear in docs via includecode then you can have the Tech Writer use git_revision="lm-rc-snippets" to stage from your branch and then make a note to remove that after launch.

[egilmorez]

Sam's right about git_revision, but it comes with a caveat: you can't use the newer, registry-based named snippets with that flag. So I'd resist that unless there's a big rush.

[samtstern]

@egilmorez actually git_revision is totally compatible with the Snippet Registry and there's even a refactoring workflow to undo it!
https://g3doc.corp.google.com/devrel/tools/includecode/g3doc/guide-refactor-snippets.md?cl=head#option-2-migrate-branches

[egilmorez]

Check you guys out! I'll try that today; I'm an excellent test for ease-of-use criteria :D

[lahirumaramba]

@samtstern @hiranya911 :
Updated admin/build.gradle to point to the latest firebase-admin v7.1.0. Had to update Notification to use the builder() in FirebaseMessagingSnippets. Let me know if you would rather have us done that in a separate PR (the upgrade and changes to FirebaseMessagingSnippets) and then follow up with this PR.
Thank you!