feat(employee): add action to remove employee from project (SCRUM-23) (!35)

Reviewed-on: #35
Reviewed-by: Phan Huy Tran <ptran@noreply.localhost>
Co-authored-by: Jan Klattenhoff <jan@kjan.de>
Co-committed-by: Jan Klattenhoff <jan@kjan.de>

src/main/java/de/szut/lf8_starter/project/action/employee/RemoveEmployeeFromProjectAction.java

@@ -0,0 +1,52 @@
+package de.szut.lf8_starter.project.action.employee;
+
+import de.szut.lf8_starter.employee.EmployeeService;
+import de.szut.lf8_starter.project.ProjectEntity;
+import de.szut.lf8_starter.project.ProjectService;
+import io.swagger.v3.oas.annotations.Operation;
+import io.swagger.v3.oas.annotations.media.Content;
+import io.swagger.v3.oas.annotations.responses.ApiResponse;
+import io.swagger.v3.oas.annotations.responses.ApiResponses;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.Optional;
+
+@RestController
+public class RemoveEmployeeFromProjectAction {
+    private final ProjectService projectService;
+    private final EmployeeService employeeService;
+
+    public RemoveEmployeeFromProjectAction(ProjectService projectService, EmployeeService employeeService) {
+        this.projectService = projectService;
+        this.employeeService = employeeService;
+    }
+
+    @Operation(summary = "Remove an employee from a project")
+    @ApiResponses(value = {
+            @ApiResponse(responseCode = "204", description = "Employee removed from project"),
+            @ApiResponse(responseCode = "404", description = "Project or employee not found", content = @Content)
+    })
+    @DeleteMapping("/projects/{projectId}/employees/{employeeId}")
+    public ResponseEntity<Object> remove(
+            @PathVariable Long projectId,
+            @PathVariable Long employeeId,
+            @RequestHeader("Authorization") String accessToken
+    ) {
+        Optional<ProjectEntity> project = this.projectService.findById(projectId);
+
+        if (project.isEmpty()) {
+            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
+        }
+
+        if (!this.employeeService.employeeExists(accessToken, employeeId)) {
+            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
+        }
+
+        project.get().getEmployees().remove(employeeId);
+        this.projectService.update(project.get());
+
+        return new ResponseEntity<>(HttpStatus.NO_CONTENT);
+    }
+}