feat(projections): resource counters (#9979)

# Which Problems Are Solved

Add the ability to keep track of the current counts of projection
resources. We want to prevent calling `SELECT COUNT(*)` on tables, as
that forces a full scan and sudden spikes of DB resource uses.

# How the Problems Are Solved

- A resource_counts table is added
- Triggers that increment and decrement the counted values on inserts
and deletes
- Triggers that delete all counts of a table when the source table is
TRUNCATEd. This is not in the business logic, but prevents wrong counts
in case someone want to force a re-projection.
- Triggers that delete all counts if the parent resource is deleted
- Script to pre-populate the resource_counts table when a new source
table is added.

The triggers are reusable for any type of resource, in case we choose to
add more in the future.
Counts are aggregated by a given parent. Currently only `instance` and
`organization` are defined as possible parent. This can later be
extended to other types, such as `project`, should the need arise.

I deliberately chose to use `parent_id` to distinguish from the
de-factor `resource_owner` which is usually an organization ID. For
example:

- For users the parent is an organization and the `parent_id` matches
`resource_owner`.
- For organizations the parent is an instance, but the `resource_owner`
is the `org_id`. In this case the `parent_id` is the `instance_id`.
- Applications would have a similar problem, where the parent is a
project, but the `resource_owner` is the `org_id`


# Additional Context

Closes https://github.com/zitadel/zitadel/issues/9957

internal/query/resource_counts.go

@@ -0,0 +1,61 @@
+package query
+
+import (
+	"context"
+	"database/sql"
+	_ "embed"
+	"time"
+
+	"github.com/zitadel/zitadel/internal/domain"
+	"github.com/zitadel/zitadel/internal/telemetry/tracing"
+	"github.com/zitadel/zitadel/internal/zerrors"
+)
+
+var (
+	//go:embed resource_counts_list.sql
+	resourceCountsListQuery string
+)
+
+type ResourceCount struct {
+	ID         int // Primary key, used for pagination
+	InstanceID string
+	TableName  string
+	ParentType domain.CountParentType
+	ParentID   string
+	Resource   string
+	UpdatedAt  time.Time
+	Amount     int
+}
+
+// ListResourceCounts retrieves all resource counts.
+// It supports pagination using lastID and limit parameters.
+//
+// TODO: Currently only a proof of concept, filters may be implemented later if required.
+func (q *Queries) ListResourceCounts(ctx context.Context, lastID, limit int) (result []ResourceCount, err error) {
+	ctx, span := tracing.NewSpan(ctx)
+	defer func() { span.EndWithError(err) }()
+
+	err = q.client.QueryContext(ctx, func(rows *sql.Rows) error {
+		for rows.Next() {
+			var count ResourceCount
+			err := rows.Scan(
+				&count.ID,
+				&count.InstanceID,
+				&count.TableName,
+				&count.ParentType,
+				&count.ParentID,
+				&count.Resource,
+				&count.UpdatedAt,
+				&count.Amount)
+			if err != nil {
+				return zerrors.ThrowInternal(err, "QUERY-2f4g5", "Errors.Internal")
+			}
+			result = append(result, count)
+		}
+		return nil
+	}, resourceCountsListQuery, lastID, limit)
+	if err != nil {
+		return nil, zerrors.ThrowInternal(err, "QUERY-3f4g5", "Errors.Internal")
+	}
+	return result, nil
+}