Use OAuth2 token instead of server key for v1

[erimicel]

Added this PR thanks to @aap17 's change
#122 (comment)

Apps using the deprecated FCM legacy APIs for HTTP and XMPP should migrate to the HTTP v1 API at the earliest opportunity. Sending messages (including upstream messages) with those APIs was deprecated on June 20, 2023, and shutdown begins on July 22, 2024.

https://firebase.google.com/docs/cloud-messaging/migrate-v1
Before
Authorization: key=AIzaSyZ-1u...0GBYzPu7Udno5aA

After
Authorization: Bearer ya29.ElqKBGN2Ri_Uz...HnS_uNreA

This is already breaking change for sending messages via legacy api and should be removed;

Breaking Changes

• Remove deprecated API_KEY
• Remove deprecated send method
• Remove deprecated send_with_notification_key method
• Remove subscribe_instance_id_to_topic method
• Remove unsubscribe_instance_id_from_topic method
• Remove batch_subscribe_instance_ids_to_topic method
• Remove batch_unsubscribe_instance_ids_from_topic method

Supported Features

• Add HTTP v1 API support for send_to_topic_condition method
• Add HTTP v1 API support for send_to_topic method

TODO

• Adding tests for failing responses

[sabman]

@erimicel thanks for doing this. Could you also look at the README.md and review if the docs are up-to-date with this PR. We can then cut a new version. Since its not backwards compatible we will cut a new version: 2.0.0

[erimicel]

@erimicel thanks for doing this. Could you also look at the README.md and review if the docs are up-to-date with this PR. We can then cut a new version. Since its not backwards compatible we will cut a new version: 2.0.0

@sabman I've added a more detailed README. The core changes are listed below—could you review and let me know if they look sensible to you?

The PR also has several styling issues flagged. Let me know if you think those need to be addressed.

I performed a real production environment test with the given changes for each method, and all looks fine at the moment.

Breaking Changes

• Remove deprecated API_KEY
• Remove deprecated send method
• Remove deprecated send_with_notification_key method
• Remove subscribe_instance_id_to_topic method as dup of topic_subscription method
• Remove unsubscribe_instance_id_from_topic method as dup of topic_unsubscription method
• Remove batch_subscribe_instance_ids_to_topic method as dup of topic_bath_subscription method
• Remove batch_unsubscribe_instance_ids_from_topic method as dup of topic_bath_unsubscription method

Supported Features

• Add HTTP v1 API support for send_to_topic_condition method
• Add HTTP v1 API support for send_to_topic method

We could leave the duplicated topic subscription methods in place and soft delete the api_key. However, if we release a new version, it might be a good opportunity for cleanup. But removing API_KEY will definitely break client initializers for everybody, so I am not sure.

[tiendo1011]

@AllanQ can we merge this?

[tiendo1011]

@sabman can we merge this?

[AllanQ]

@AllanQ can we merge this?

@tiendo1011,
I am not authorized to make the decision.

[sabman]

Just running tests will merge shortly.

[sabman]

• new release now published https://rubygems.org/gems/fcm
• https://github.com/decision-labs/fcm/releases/tag/v2.0.0

Thanks to all the awesome contributors!