refactor: plugins

[chesedo]

This turns our service feature flags into separate crates. The long game here will be to allow vendors to write their own plugins...

TODO

• Update CI

Breaking changes

This changes the main function argument attributes yet again 😃 . These changes are as follow:

Old attribute	New attribute
shared::Postgres	shuttle_shared_db::Postgres
shared::MongoDb	shuttle_shared_db::MongoDb
aws::rds::Postgres	shuttle_aws_rds::Postgres
aws::rds::MySql	shuttle_aws_rds::MySql
aws::rds::MariaDB	shuttle_aws_rds::MariaDB
persist	shuttle_persist::Persist

The old feature flag on shuttle_service also needs to be replaced with the following crates definitions:

Old feature flag	Extra crate definition
sqlx-postgres	shuttle-shared-db = { version = "0.5.2", features = ["postgres"] }
mongo-integration	shuttle-shared-db = { version = "0.5.2", features = ["mongo"] }
sqlx-aws-postgres	shuttle-aws-rds = { version = "0.5.2", features = ["postgres"] }
sqlx-aws-mysql	shuttle-aws-rds = { version = "0.5.2", features = ["mysql"] }
sqlx-aws-mariadb	shuttle-aws-rds = { version = "0.5.2", features = ["mariadb"] }
secrets	shuttle-secrets = "0.5.2"
persist	shuttle-persist = "0.5.2"

[brokad]

Holy conflict mackerel! I hope I resolved this without creating more issues (apart from the ones outlined below, due to the time difference between when this was introduced and support for additional resources we have added since then).

Couple more things not specifically pointed at in the comments below:

• Web frameworks do not seem to have been modularised at all?
• The CLI is missing a small tweak for secrets I think
• Serenity is not modularised either (due to time difference)
• The modules don't seem to call on their dependencies through fully qualified versions, so I guess this will need to be added before publishing
• On that topic, will the publish scripts handle the version strings in the new crates correctly?