Rename storage certificate cache

This cache is used only for ACME certificates.

Being explicit is always better.

storage/cache.go

@@ -1,63 +0,0 @@
-// Copyright 2020 Dave Marquard. All rights reserved.
-// Use of this source code is governed by the Apache 2.0
-// license that can be found in the LICENSE file.
-
-package storage // import "miniflux.app/storage"
-
-import (
-	"context"
-	"database/sql"
-
-	"golang.org/x/crypto/acme/autocert"
-)
-
-// Making sure that we're adhering to the autocert.Cache interface.
-var _ autocert.Cache = (*Cache)(nil)
-
-// Cache provides a SQL backend to the autocert cache.
-type Cache struct {
-	storage *Storage
-}
-
-// NewCache creates an cache instance that can be used with autocert.Cache.
-// It returns any errors that could happen while connecting to SQL.
-func NewCache(storage *Storage) *Cache {
-	return &Cache{
-		storage: storage,
-	}
-}
-
-// Get returns a certificate data for the specified key.
-// If there's no such key, Get returns ErrCacheMiss.
-func (c *Cache) Get(ctx context.Context, key string) ([]byte, error) {
-	query := `SELECT data::bytea FROM acme_cache WHERE key = $1`
-	var data []byte
-	err := c.storage.db.QueryRowContext(ctx, query, key).Scan(&data)
-	if err == sql.ErrNoRows {
-		return nil, autocert.ErrCacheMiss
-	}
-
-	return data, err
-}
-
-// Put stores the data in the cache under the specified key.
-func (c *Cache) Put(ctx context.Context, key string, data []byte) error {
-	query := `INSERT INTO acme_cache (key, data, updated_at) VALUES($1, $2::bytea, now())
-	          ON CONFLICT (key) DO UPDATE SET data = $2::bytea, updated_at = now()`
-	_, err := c.storage.db.ExecContext(ctx, query, key, data)
-	if err != nil {
-		return err
-	}
-	return nil
-}
-
-// Delete removes a certificate data from the cache under the specified key.
-// If there's no such key in the cache, Delete returns nil.
-func (c *Cache) Delete(ctx context.Context, key string) error {
-	query := `DELETE FROM acme_cache WHERE key = $1`
-	_, err := c.storage.db.ExecContext(ctx, query, key)
-	if err != nil {
-		return err
-	}
-	return nil
-}