do not omit "empty" booleans in yaml output

The "empty" boolean is the false value. This means that values of false will not
be present in the YAML output. As such they won't be displayed in the config
section on the Status overview page (/#/status), which can be especially
confusing for the SMTPRequireTLS (smtp_require_tls) field of the configuration
as this one will default to true.

config/config.go

@@ -550,7 +550,7 @@ type GlobalConfig struct {
 	SMTPAuthPassword Secret     `yaml:"smtp_auth_password,omitempty" json:"smtp_auth_password,omitempty"`
 	SMTPAuthSecret   Secret     `yaml:"smtp_auth_secret,omitempty" json:"smtp_auth_secret,omitempty"`
 	SMTPAuthIdentity string     `yaml:"smtp_auth_identity,omitempty" json:"smtp_auth_identity,omitempty"`
-	SMTPRequireTLS   bool       `yaml:"smtp_require_tls,omitempty" json:"smtp_require_tls,omitempty"`
+	SMTPRequireTLS   bool       `yaml:"smtp_require_tls" json:"smtp_require_tls,omitempty"`
 	SlackAPIURL      *SecretURL `yaml:"slack_api_url,omitempty" json:"slack_api_url,omitempty"`
 	PagerdutyURL     *URL       `yaml:"pagerduty_url,omitempty" json:"pagerduty_url,omitempty"`
 	OpsGenieAPIURL   *URL       `yaml:"opsgenie_api_url,omitempty" json:"opsgenie_api_url,omitempty"`
@@ -579,7 +579,7 @@ type Route struct {
 
 	Match    map[string]string `yaml:"match,omitempty" json:"match,omitempty"`
 	MatchRE  MatchRegexps      `yaml:"match_re,omitempty" json:"match_re,omitempty"`
-	Continue bool              `yaml:"continue,omitempty" json:"continue,omitempty"`
+	Continue bool              `yaml:"continue" json:"continue,omitempty"`
 	Routes   []*Route          `yaml:"routes,omitempty" json:"routes,omitempty"`
 
 	GroupWait      *model.Duration `yaml:"group_wait,omitempty" json:"group_wait,omitempty"`

config/notifiers.go

@@ -340,15 +340,15 @@ type SlackConfig struct {
 	Pretext     string         `yaml:"pretext,omitempty" json:"pretext,omitempty"`
 	Text        string         `yaml:"text,omitempty" json:"text,omitempty"`
 	Fields      []*SlackField  `yaml:"fields,omitempty" json:"fields,omitempty"`
-	ShortFields bool           `yaml:"short_fields,omitempty" json:"short_fields,omitempty"`
+	ShortFields bool           `yaml:"short_fields" json:"short_fields,omitempty"`
 	Footer      string         `yaml:"footer,omitempty" json:"footer,omitempty"`
 	Fallback    string         `yaml:"fallback,omitempty" json:"fallback,omitempty"`
 	CallbackID  string         `yaml:"callback_id,omitempty" json:"callback_id,omitempty"`
 	IconEmoji   string         `yaml:"icon_emoji,omitempty" json:"icon_emoji,omitempty"`
 	IconURL     string         `yaml:"icon_url,omitempty" json:"icon_url,omitempty"`
 	ImageURL    string         `yaml:"image_url,omitempty" json:"image_url,omitempty"`
 	ThumbURL    string         `yaml:"thumb_url,omitempty" json:"thumb_url,omitempty"`
-	LinkNames   bool           `yaml:"link_names,omitempty" json:"link_names,omitempty"`
+	LinkNames   bool           `yaml:"link_names" json:"link_names,omitempty"`
 	MrkdwnIn    []string       `yaml:"mrkdwn_in,omitempty" json:"mrkdwn_in,omitempty"`
 	Actions     []*SlackAction `yaml:"actions,omitempty" json:"actions,omitempty"`
 }
@@ -534,7 +534,7 @@ type PushoverConfig struct {
 	Priority string   `yaml:"priority,omitempty" json:"priority,omitempty"`
 	Retry    duration `yaml:"retry,omitempty" json:"retry,omitempty"`
 	Expire   duration `yaml:"expire,omitempty" json:"expire,omitempty"`
-	HTML     bool     `yaml:"html,omitempty" json:"html,omitempty"`
+	HTML     bool     `yaml:"html" json:"html,omitempty"`
 }
 
 // UnmarshalYAML implements the yaml.Unmarshaler interface.