refactor(v2): init events (#7823)

creates events structures for initial projections and read models

internal/v2/eventstore/postgres/query.go

@@ -3,6 +3,7 @@ package postgres
 import (
 	"context"
 	"database/sql"
+	"encoding/json"
 	"slices"
 
 	"github.com/zitadel/logging"
@@ -38,7 +39,7 @@ func executeQuery(ctx context.Context, tx database.Querier, stmt *database.State
 	}
 
 	err = database.MapRowsToObject(rows, func(scan func(dest ...any) error) error {
-		e := new(eventstore.Event[eventstore.StoragePayload])
+		e := new(eventstore.StorageEvent)
 
 		var payload sql.Null[[]byte]
 
@@ -59,7 +60,12 @@ func executeQuery(ctx context.Context, tx database.Querier, stmt *database.State
 		if err != nil {
 			return err
 		}
-		e.Payload = unmarshalPayload(payload.V)
+		e.Payload = func(ptr any) error {
+			if len(payload.V) == 0 {
+				return nil
+			}
+			return json.Unmarshal(payload.V, ptr)
+		}
 		eventCount++
 
 		return reducer.Reduce(e)