Add post video storage.

internal/store/post_test.go

@@ -338,6 +338,36 @@ func TestMemoryPostImages(t *testing.T) {
 	if err := mem.CreatePost(ctx, tooMany); !errors.Is(err, ErrInvalidPost) {
 		t.Fatalf("five-image create error = %v, want ErrInvalidPost", err)
 	}
+
+	withVideo := &Post{
+		AuthorID: homeowner.ID,
+		Title:    "With video",
+		Body:     "Four photos and a clip.",
+		Images: append(validPostImages(4), PostImage{
+			ID:        "clip-1",
+			ObjectKey: "posts/clip-1.mp4",
+			PublicURL: "https://cdn.example/clip-1.mp4",
+			Kind:      MediaKindVideo,
+		}),
+	}
+	if err := mem.CreatePost(ctx, withVideo); err != nil {
+		t.Fatalf("four images and one video: %v", err)
+	}
+	if withVideo.Images[4].Kind != MediaKindVideo || withVideo.Images[4].Position != 4 {
+		t.Fatalf("video not stored: %+v", withVideo.Images[4])
+	}
+	twoVideos := &Post{
+		AuthorID: homeowner.ID,
+		Title:    "Two clips",
+		Body:     "Not allowed.",
+		Images: []PostImage{
+			{ObjectKey: "posts/a.mp4", PublicURL: "https://cdn.example/a.mp4", Kind: MediaKindVideo},
+			{ObjectKey: "posts/b.mp4", PublicURL: "https://cdn.example/b.mp4", Kind: MediaKindVideo},
+		},
+	}
+	if err := mem.CreatePost(ctx, twoVideos); !errors.Is(err, ErrInvalidPost) {
+		t.Fatalf("two-video create error = %v, want ErrInvalidPost", err)
+	}
 }
 
 func validPostImages(count int) []PostImage {