Deploy: main into prod (#343)

Brings `prod`, which upaas deploys, up to `main` at `9cf9cdd`, the merge of #321. `prod` was cut from `main` at `251cb3d` (1.0.0b1).

What it deploys is everything listed in #321. For running it:

- With `WEBHOOKER_ENVIRONMENT` unset, the instance runs as `prod` and sends no `Access-Control-Allow-Origin: *`.
- Each event database gains its new indexes the first time it is opened after the upgrade.
- `webhooker_delivery_retries_total` no longer counts a circuit breaker holding back a delivery that is already `retrying`.

Not in this PR yet: #340, in which the container sets its own data directory owner and mode before start. It is in progress on `next`. Once it reaches `main`, this PR carries it, because the PR follows `main`.

Model: opus-5-5
Co-authored-by: Jeffrey Paul <1+sneak@noreply.example.org>
Reviewed-on: #343

internal/database/model_delivery.go

@@ -1,5 +1,7 @@
 package database
 
+import "gorm.io/gorm"
+
 // DeliveryStatus represents the status of a delivery
 type DeliveryStatus string
 
@@ -29,12 +31,19 @@ func (s DeliveryStatus) Terminal() bool {
 }
 
 // Delivery represents a delivery attempt for an event to a target
+//
+//nolint:lll // a struct tag cannot wrap
 type Delivery struct {
 	BaseModel
 
-	EventID  string         `gorm:"type:uuid;not null"         json:"eventId"`
-	TargetID string         `gorm:"type:uuid;not null"         json:"targetId"`
-	Status   DeliveryStatus `gorm:"not null;default:'pending'" json:"status"`
+	EventID  string         `gorm:"type:uuid;not null;index:idx_deliveries_event_id,priority:1"       json:"eventId"`
+	TargetID string         `gorm:"type:uuid;not null"                                                json:"targetId"`
+	Status   DeliveryStatus `gorm:"not null;default:'pending';index:idx_deliveries_status,priority:1" json:"status"`
+
+	// DeletedAt repeats the BaseModel field only to be the second column
+	// of the event_id and status indexes, for the reason DeliveryResult
+	// gives.
+	DeletedAt gorm.DeletedAt `gorm:"index:idx_deliveries_event_id,priority:2;index:idx_deliveries_status,priority:2" json:"deletedAt,omitzero"`
 
 	// Relations
 	Event           Event            `json:"event,omitzero"`