Best practices review before first release

# What is currently missing?

Some things are easy to change before the first release, and tricky to change afterwards! We should do a thorough final review of the source and sink before releasing 1.0.0.

# How could this be improved?

* Are the configuration properties consistent and helpfully named?
- Is the site documentation generated correctly with useful descriptions and examples?
* Are the source, sink and common modules consistent, and follow our best practices?
- Do we have a BUILD.md and/or CONTRIBUTING.md to encourage the community to contribute?
* Are class names and packages coherent?
- `io.aiven.kafka.connect.salesforce.common`
- `io.aiven.kafka.connect.salesforce.source`
- `io.aiven.kafka.connect.salesforce.sink`
* No SNAPSHOT dependencies or dependencies with vulnerabilities.
* Are we using the https://github.com/Aiven-Open/aiven-kafka-connector-framework to it's advantage?
- Are there common functions that should be pushed up into this common code?
- See #19 as an example.

# Is this a feature you would work on yourself?

* [ ] I plan to open a pull request for this feature