feedkit: split the former maximumdirect.net/weatherd project in two.

feedkit now contains a reusable core, while weatherfeeder is a concrete implementation that includes weather-specific functions.

sinks/postgres.go

@@ -0,0 +1,37 @@
+package sinks
+
+import (
+	"context"
+	"fmt"
+
+	"gitea.maximumdirect.net/ejr/feedkit/config"
+	"gitea.maximumdirect.net/ejr/feedkit/event"
+)
+
+type PostgresSink struct {
+	name string
+	dsn  string
+}
+
+func NewPostgresSinkFromConfig(cfg config.SinkConfig) (Sink, error) {
+	dsn, err := requireStringParam(cfg, "dsn")
+	if err != nil {
+		return nil, err
+	}
+	return &PostgresSink{name: cfg.Name, dsn: dsn}, nil
+}
+
+func (p *PostgresSink) Name() string { return p.name }
+
+func (p *PostgresSink) Consume(ctx context.Context, e event.Event) error {
+	_ = ctx
+
+	// Boundary validation: if something upstream violated invariants,
+	// surface it loudly rather than printing partial nonsense.
+	if err := e.Validate(); err != nil {
+		return fmt.Errorf("rabbitmq sink: invalid event: %w", err)
+	}
+
+	// TODO implement Postgres transaction
+	return nil
+}