Store a target's settings as columns (closes #543)

A target's settings move from the per-type JSON string in
targets.config to columns: url, headers, timeout_seconds,
forward_query, archive_expiry and archive_rotation. A column a type
does not use stays empty. headers holds the header map as JSON text
through GORM's JSON serializer, and archive_expiry holds a
time.Duration, 0 meaning never, so nothing that reads a target parses
it. The forms check each setting once, with the same refusals and
messages, and the edit form is filled from the columns, so the
per-type config structs, their parsers and the "could not be read"
branches are gone. A delivery task carries the six settings in place
of the JSON string.

Model: opus-5-5

internal/database/model_target.go

@@ -1,5 +1,7 @@
 package database
 
+import "time"
+
 // TargetType represents the type of delivery target
 type TargetType string
 
@@ -11,7 +13,9 @@ const (
 	TargetTypeSlack    TargetType = "slack"
 )
 
-// Target represents a delivery target for a webhook
+// Target represents a delivery target for a webhook. Its settings
+// are the fields from URL to ArchiveRotation; each type uses some of
+// them, and the ones a type does not use stay empty.
 type Target struct {
 	BaseModel
 
@@ -20,14 +24,35 @@ type Target struct {
 	Type      TargetType `gorm:"not null"           json:"type"`
 	Active    bool       `gorm:"default:true"       json:"active"`
 
-	// Configuration fields (JSON stored based on type).
+	// URL is where an http or slack target sends each event.
 	//
-	// json:"-" because the blob holds the target's credential — a
-	// Slack incoming-webhook URL, or an http destination whose path
-	// segments are the secret. delivery.TargetView is the masking
-	// barrier for the HTML path; this tag is the barrier for any
-	// handler that marshals the model itself.
-	Config string `gorm:"type:text" json:"-"` // JSON configuration
+	// json:"-" because the URL is the target's credential: a Slack
+	// incoming-webhook URL, or an http destination whose path segments
+	// are the secret. delivery.TargetView is the masking barrier for
+	// the HTML path; this tag is the barrier for any handler that
+	// marshals the model itself.
+	URL string `json:"-"`
+
+	// Headers is an http target's extra request headers, name to
+	// value, stored as JSON text. json:"-" for the same reason as URL:
+	// a header value is routinely an authorization token.
+	Headers map[string]string `gorm:"serializer:json" json:"-"`
+
+	// TimeoutSeconds is an http target's per-request timeout; 0 uses
+	// the delivery engine's shared client timeout.
+	TimeoutSeconds int `json:"timeoutSeconds,omitempty"`
+
+	// ForwardQuery passes each event's query string on to an http
+	// target, appended to URL. Off, URL is sent exactly as stored.
+	ForwardQuery bool `json:"forwardQuery,omitempty"`
+
+	// ArchiveExpiry is how long a database target keeps each archived
+	// event; 0 keeps them forever.
+	ArchiveExpiry time.Duration `json:"archiveExpiry,omitempty"`
+
+	// ArchiveRotation is how often a database target starts a new
+	// archive file: none, monthly, daily or hourly.
+	ArchiveRotation string `json:"archiveRotation,omitempty"`
 
 	// MaxAttempts is how many times an HTTP or Slack target attempts
 	// each delivery in all, at least 1. 1 is a single attempt with no