Common Code for Backend Services

[rmandlx]

We need a Gradle Project that contains common code for all services. The Services can include this project and access the code. The project should use the package: com.bikenest.common

Components of the Common Project:

• Definition of Interfaces for all Endpoints (e.g. currently the Booking service has the /booking/add endpoint that accepts a NewReservationPOJO Object, that contains the BikenestId, the StartDateTime and the EndDateTime of a new reservation. This Class should rather be defined in the common code base, so that other service do not have to define it themselves, if they want to communicate with the Booking service.)
• Maybe more spring specific stuff like even declaring FeignClients. They can be used to access endpoints of other services, but since they would be used by Autowiring, Im not sure if it would work, if they are defined in another project. This has to be tested!
• The JWTAuthenticationFilter, because essentially it would be the same for each service.
• The JWT Claims Object (doesn't exist so far?, an object that defines what claims are stored inside the JWT)

[rmandlx]

So I found out to include another project via gradle, you have to use this inside "settings.gradle": includeBuild "../common"

It is also possible to specify a root project for the Backend, that includes all sub projects and handles building.

[rmandlx]

The last commit 7c7f22c
allows the service projects to be built individually. It was really complicated getting it to work: You can define the used plugins inside settings.gradle So if you define them inside the root project, then you are not allowed to define the plugin versions inside the build.gradle files of the subprojects. But if you want to build the subprojects individually, it wont work if you don't define the versions. Thats why I had to change the settings.gradle of each project and also define the plugin versions there.

And if you build a service individually, it also won't know about the common project, thats why you also have to specify include ':common' project(':common').projectDir = new File('../common') inside the settings.gradle of each project...

[rmandlx]

This will be integrated into the main branch with #83.