refactor: rename Processor to Webhook and Webhook to Entrypoint

The top-level entity that groups entrypoints and targets is now called
Webhook (was Processor). The inbound URL endpoint entity is now called
Entrypoint (was Webhook). This rename affects database models, handler
comments, routes, and README documentation.

closes #12

internal/database/model_event.go

@@ -1,11 +1,11 @@
 package database
 
-// Event represents a webhook event
+// Event represents a captured webhook event
 type Event struct {
 	BaseModel
 
-	ProcessorID string `gorm:"type:uuid;not null" json:"processor_id"`
-	WebhookID   string `gorm:"type:uuid;not null" json:"webhook_id"`
+	WebhookID    string `gorm:"type:uuid;not null" json:"webhook_id"`
+	EntrypointID string `gorm:"type:uuid;not null" json:"entrypoint_id"`
 
 	// Request data
 	Method      string `gorm:"not null" json:"method"`
@@ -14,7 +14,7 @@ type Event struct {
 	ContentType string `json:"content_type"`
 
 	// Relations
-	Processor  Processor  `json:"processor,omitempty"`
 	Webhook    Webhook    `json:"webhook,omitempty"`
+	Entrypoint Entrypoint `json:"entrypoint,omitempty"`
 	Deliveries []Delivery `json:"deliveries,omitempty"`
 }