feat: add get group by faculty id

Endpoint/Controllers/V1/GroupController.cs

@@ -80,5 +80,29 @@ namespace Mirea.Api.Endpoint.Controllers.V1
                 CourseNumber = GetCourseNumber(result.Name)
             });
         }
+
+        /// <summary>
+        /// Retrieves a list of groups by faculty ID.
+        /// </summary>
+        /// <param name="id">The ID of the faculty.</param>
+        /// <returns>A list of groups belonging to the specified faculty.</returns>
+        [HttpGet("{id:int}")]
+        [ProducesResponseType(StatusCodes.Status200OK)]
+        [BadRequestResponse]
+        [NotFoundResponse]
+        public async Task<ActionResult<List<GroupResponse>>> GetByFaculty(int id)
+        {
+            var result = await mediator.Send(new GetGroupListQuery());
+
+            return Ok(result.Groups
+                .Where(g => g.FacultyId == id)
+                .Select(g => new GroupResponse()
+                {
+                    Id = g.Id,
+                    Name = g.Name,
+                    CourseNumber = GetCourseNumber(g.Name),
+                    FacultyId = g.FacultyId
+                }));
+        }
     }
 }