refactor: corrects operationIds in ewm service specs

[TimoshenkoAleksey]

Prerequisite: It is highly recommended to merge yandex-praktikum/java-explore-with-me#22 changes, since generation via swagger-codegen-maven-plugin does not work correctly for original ewm-main-service-spec.json file.

In case of code generation via swagger-codegen-maven-plugin there are several problems with operationIds provided in ewm-main-service-spec.json file (see demo pom.xml in terekhovmv/java-explore-with-me-fixes@da018e0).

1. Some of operationIds contain numeric suffixes, and this suffixes appear in methods of generated *Api interfaces (getEvents_2, getEvent_1). Solution: remove suffixes at least.
2. There is no consistency in naming (delete / deleteCompilation, registerUser / addEvent / saveCompilation). Solution: provide consistent naming.
3. Since *Api interfaces are generated for top level endpoint components (/users/* => UsersApi) there are problems with identifying endpoint methods for different roles (e.g. cancelRequest and changeRequestStatus in the UsersApi interface). Solution: put the role as prefix in operationIds.
4. Since operationIds must be unique among all operations described in your API (see https://swagger.io/docs/specification/paths-and-operations/), we should provide enough global descriptive names (delete or getEvent_1 does not work).

Tabular view of changes proposed in this PR:

Method	Original operationId	Recommended operationId
PUBLIC
GET /categories	getCategories	getCategories (no changes)
GET /categories/{catId}	getCategory	getCategory (no changes)
GET /compilations	getCompilations	getCompilations (no changes)
GET /compilations/{compId}	getCompilation	getCompilation (no changes)
GET /events	getEvents_1	findEvents
GET /events/{id}	getEvent_1	getEvent
ADMIN
GET /admin/users	getUsers	adminGetUsers
POST /admin/users	registerUser	adminAddUser
DELETE /admin/users/{userId}	delete	adminRemoveUser
POST /admin/categories	addCategory	adminAddCategory
DELETE /admin/categories/{catId}	deleteCategory	adminRemoveCategory
PATCH /admin/categories/{catId}	updateCategory	adminUpdateCategory
GET /admin/events	getEvents_2	adminFindEvents
PATCH /admin/events/{eventId}	updateEvent_1	adminUpdateEvent
POST /admin/compilations	saveCompilation	adminAddCompilation
DELETE /admin/compilations/{compId}	deleteCompilation	adminRemoveCompilation
PATCH /admin/compilations/{compId}	updateCompilation	adminUpdateCompilation
INITIATOR
GET /users/{userId}/events	getEvents	initiatorGetEvents
GET /users/{userId}/events/{eventId}	getEvents	initiatorGetEvent
POST /users/{userId}/events	addEvent	initiatorAddEvent
PATCH /users/{userId}/events/{eventId}	updateEvent	initiatorUpdateEvent
GET /users/{userId}/events/{eventId}/requests	getEventParticipants	initiatorGetEventRequests
PATCH /users/{userId}/events/{eventId}/requests	changeRequestStatus	initiatorChangeRequestStatus
PARTICIPANT
GET /users/{userId}/requests	getUserRequests	participantGetRequests
POST /users/{userId}/requests	addParticipationRequest	participantAddRequest
PATCH /users/{userId}/requests/{requestId}/cancel	cancelRequest	participantCancelRequest