[MM-13747] Add ability to list users to plugin API (#10102)

* add GetUsers in plugin api

* change GetUsers(page int, perPage int) ([]*model.User, *model.AppError) to GetUsers(options *model.UserGetOptions) ([]*model.User, *model.AppError)

* Update GetUsers doc

Co-Authored-By: dom3k <szeptweb@gmail.com>

* Update doc in plugin/api.go

Co-Authored-By: dom3k <szeptweb@gmail.com>

* correct database initialization for the test

* Update plugin/api.go

Co-Authored-By: dom3k <szeptweb@gmail.com>

plugin/api.go

@@ -55,6 +55,11 @@ type API interface {
 	// DeleteUser deletes a user.
 	DeleteUser(userId string) *model.AppError
 
+	// GetUsers a list of users based on search options.
+	//
+	// Minimum server version: 5.10
+	GetUsers(*model.UserGetOptions) ([]*model.User, *model.AppError)
+
 	// GetUser gets a user.
 	GetUser(userId string) (*model.User, *model.AppError)