Add PostgreSQL support (#23)

Signed-off-by: Julien Riou <julien@riou.xyz>

config.go

@@ -8,6 +8,7 @@ import (
 
 // Config to store JSON configuration
 type Config struct {
+	DatabaseConfig `json:"database"`
 	TwitterConfig  `json:"twitter"`
 	TelegramConfig `json:"telegram"`
 	APIConfig      `json:"api"`
@@ -18,6 +19,12 @@ type Config struct {
 	BrowserAddress string   `json:"browser_address"`
 }
 
+// DatabaseConfig to store database configuration
+type DatabaseConfig struct {
+	Type string `json:"type"`
+	DSN  string `json:"dsn"`
+}
+
 // TwitterConfig to store Twitter API secrets
 type TwitterConfig struct {
 	ConsumerKey       string              `json:"consumer_key"`
@@ -96,6 +103,11 @@ func (c *Config) HasURLs() bool {
 	return len(c.URLs) > 0
 }
 
+// HasDatabase returns true when database has been configured
+func (c *Config) HasDatabase() bool {
+	return c.DatabaseConfig.Type != "" && c.DatabaseConfig.DSN != ""
+}
+
 // HasAmazon returns true when Amazon has been configured
 func (c *Config) HasAmazon() bool {
 	var hasKeys, hasSearches, hasMarketplaces bool