Develop

See merge request !25

 add post item endpoint

See merge request !24

 rename ref to id in Item model

See merge request !22

 add error controller

See merge request !21

 Use dependency injection for categories controller

See merge request !19

Merge branch 'feature/refactor_controllers_to_use_repositories' into 'feature/use_dependency_injection_for_categories'

 split DatabaseSystem.java to multiple repositories #5

See merge request !20

Fixed Javadoc. #1

See merge request !18

Added sample login form. #4

See merge request !17

Started Web interface. #4

See merge request !16

Internationalization.

See merge request !15

Documentation overhaul. #1

See merge request !14

Attempt to get OpenAPI specification working.

See merge request !13

Javadoc updates.

See merge request !12