feat(billing): Support -/+ infinity

This updates the billing repository to use timestmap.Timestamp when
constructing the queries to retrieve monthly active users. This allows
for specifying NegativeInfinity to easily retrieve all monthly active
user counts.

internal/billing/repository.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/hashicorp/boundary/internal/db"
+	"github.com/hashicorp/boundary/internal/db/timestamp"
 	"github.com/hashicorp/boundary/internal/errors"
 )
 
@@ -65,7 +66,7 @@ func (r *Repository) MonthlyActiveUsers(ctx context.Context, opt ...Option) ([]A
 		}
 		query = activeUsersWithStartTimeQuery
 		args = append(args,
-			sql.Named("start_time", opts.withStartTime))
+			sql.Named("start_time", timestamp.New(*opts.withStartTime)))
 	}
 	if opts.withEndTime != nil {
 		if *opts.withEndTime != time.Date(opts.withEndTime.Year(), opts.withEndTime.Month(), 1, 0, 0, 0, 0, time.UTC) {
@@ -73,7 +74,7 @@ func (r *Repository) MonthlyActiveUsers(ctx context.Context, opt ...Option) ([]A
 		}
 		query = activeUsersWithStartTimeAndEndTimeQuery
 		args = append(args,
-			sql.Named("end_time", opts.withEndTime))
+			sql.Named("end_time", timestamp.New(*opts.withEndTime)))
 	}
 
 	var activeUsers []ActiveUsers