Declare only the tables and columns pixa writes and reads (closes #310)

Removes output_content and request_cache, which nothing writes, and every
column that was written but never read: the host, path, query, content_type
and fetched_at of source_content, the content_type and created_at of
variant_content, and the status_code, error_message and fetched_at of
negative_cache.

StoreSource no longer takes the fetch result and LookupSource returns only
the source key. StoreVariant no longer takes a content type and
StoreNegative no longer takes a status code or message, so
extractStatusCode and the status constants, which only fed status_code,
are gone. Reconciliation adopts a variant file without opening it, as its
row no longer records a content type. Tests that set or checked a removed
column follow.

Model: opus-5-5

internal/imgcache/eviction_internal_test.go

@@ -16,7 +16,6 @@ import (
 
 	"modernc.org/sqlite"
 	"sneak.berlin/go/pixa/internal/database"
-	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
@@ -102,17 +101,8 @@ func storeEvictionTestSource(
 		},
 	}
 
-	result := &httpfetcher.FetchResult{
-		StatusCode:    200,
-		ContentType:   testContentTypeJPEG,
-		ContentLength: int64(len(content)),
-		Headers: map[string][]string{
-			testHeaderContentType: {testContentTypeJPEG},
-		},
-	}
-
 	key, err := cache.StoreSource(
-		context.Background(), req, bytes.NewReader(content), result,
+		context.Background(), req, bytes.NewReader(content),
 	)
 	if err != nil {
 		t.Fatalf("StoreSource(%s%s) failed: %v", host, path, err)
@@ -128,7 +118,7 @@ func storeEvictionTestVariant(
 ) {
 	t.Helper()
 
-	err := cache.StoreVariant(t.Context(), key, bytes.NewReader(content), "image/webp")
+	err := cache.StoreVariant(t.Context(), key, bytes.NewReader(content))
 	if err != nil {
 		t.Fatalf("StoreVariant(%s) failed: %v", key, err)
 	}
@@ -437,20 +427,13 @@ func assertDisabledCacheWritesAreNoOps(
 	ctx := t.Context()
 
 	err := cache.StoreVariant(
-		ctx, imagerequest.CacheKey(req), bytes.NewReader([]byte("data")), "image/webp",
+		ctx, imagerequest.CacheKey(req), bytes.NewReader([]byte("data")),
 	)
 	if err != nil {
 		t.Fatalf("StoreVariant on disabled cache must be a no-op, got error: %v", err)
 	}
 
-	result := &httpfetcher.FetchResult{
-		StatusCode:    200,
-		ContentType:   testContentTypeJPEG,
-		ContentLength: 4,
-		Headers:       map[string][]string{},
-	}
-
-	key, err := cache.StoreSource(ctx, req, bytes.NewReader([]byte("data")), result)
+	key, err := cache.StoreSource(ctx, req, bytes.NewReader([]byte("data")))
 	if err != nil {
 		t.Fatalf("StoreSource on disabled cache must be a no-op, got error: %v", err)
 	}
@@ -469,14 +452,13 @@ func assertDisabledCacheReadsAlwaysMiss(
 
 	ctx := t.Context()
 
-	key, srcType, err := cache.LookupSource(ctx, req)
+	key, err := cache.LookupSource(ctx, req)
 	if err != nil {
 		t.Fatalf("LookupSource on disabled cache failed: %v", err)
 	}
 
-	if key != "" || srcType != "" {
-		t.Errorf("LookupSource on disabled cache = (%q, %q), want empty",
-			key, srcType)
+	if key != "" {
+		t.Errorf("LookupSource on disabled cache = %q, want empty", key)
 	}
 }
 
@@ -667,9 +649,8 @@ func TestStartEvictionReconcilesAccountingWithDisk(t *testing.T) {
 
 	// An accounting row whose file is missing must be dropped.
 	_, err = cache.db.ExecContext(t.Context(),
-		`INSERT INTO variant_content (cache_key, size_bytes, content_type)
-		 VALUES (?, ?, ?)`,
-		"deadbeef0001", 700, "image/webp",
+		`INSERT INTO variant_content (cache_key, size_bytes) VALUES (?, ?)`,
+		"deadbeef0001", 700,
 	)
 	if err != nil {
 		t.Fatalf("failed to insert stale variant accounting row: %v", err)