Add option to provide pubsub configuration for topic

[marcwickenden]

Description

Provides the ability to configure the creation of the GCP PubSub topic. Specifically I wanted to be able to specify message retention. This paves the way for replaying messages to enable projections to resync.

Affected Components

• Event Bus

Related Issues

Nothing specific but begins to address projection errors. Only for GCP though.

Solution and Design

The pubsub client also has a CreateTopicWithConfig function which takes an additional argument of a TopicConfig struct. By adding an additional function to the gcp eventbus package (WithTopicOptions, copypasta of WithPubSubOptions but updates different struct property) we can supply a TopicConfig struct as an option to NewEventBus().

Steps to test and verify

1. Run TestEventBusWithConfigIntegration test in eventbus_test.go.

[coveralls]

Coverage increased (+0.02%) to 68.831% when pulling 9b8a8fd on marcwickenden:main into 1a72481 on looplab:main.