fix: check-in becomes negative

feat: add change membership to club card

feature: add client list, trainer screen,

feature: add membership list

feature: add client registration

feat: add Docker configuration

refactor: delete unnecessary folders and comments

first_commit

feat: add exception handlers

feat: add check-in for club card

test: add tests for ClientServiceImpl

test: add tests for ClubCardServiceImpl

test: add tests for ActivityTypeServiceImpl

test: add tests for MembershipServiceImpl

fix: data loss when updating

fix: objects incorrectly bound

test: add tests for TrainerServiceImpl

fix: added service interfaces

fix: exception messages and logging

fix: exception throwing and handling

fix: exception throwing and handling