1. use [staticcheck](https://staticcheck.io/) to check the code, and fix some issues.
2. use `go fmt` to format the code.
3. use `go mod tidy` clean the go mod.
Add a config setting to allow copying message fields and decorations into Google Pub/Sub attributes, making it possible to use these values for subscription filters.
Adds Google Cloud PubSub logging for status and results.
This also changes the Write interface for logging modules to add a context.Context (only used by pubsub currently).
Fixes a regression introduced in 2.1.0 in which separate log lines are
no longer output separated by a newline. Now log lines in both output
plugins will do so.
- Refactor configuration for logging to use separate plugins
- Move existing filesystem logging to filesystem plugin
- Create new AWS firehose plugin
- Update documentation around logging
