Also locks the tools versions and launches them from the packages
installed by the go mod. Otherwise, they would have to be manually
installed beforehand.
Swap direct access to the DB on the API server with an data abstraction
layer.
Implement each API type converter separately and revert changes to the
auto-generated server implementation types.
Add error return to DAL methods. Implement `Transactions`.
Add tools.go with oapi-codegen and mockgen.
https://www.jvt.me/posts/2022/06/15/go-tools-dependency-management/
Update go packages.
Issues #5, #12
Introduces the api-server/main.go, which creates the echo server,
connects it to the implemented handlers and runs it.
Fix the SQL query to retrieved transactions w/ categories.
Issues #6 and #7
