appview/db: make registration.secrets nullable and Add/DeleteKnot helpers

Signed-off-by: Anirudh Oppiliappan <[e-mail]>

appview/db/db.go

···
 		return nil
 	})
 
+	// make registrations.secret nullable for unified registration flow
+	runMigration(db, "make-registrations-secret-nullable", func(tx *sql.Tx) error {
+		// sqlite doesn't support ALTER COLUMN, so we need to recreate the table
+		_, err := tx.Exec(`
+			create table registrations_new (
+				id integer primary key autoincrement,
+				domain text not null unique,
+				did text not null,
+				secret text,
+				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
+				registered text
+			);
+
+			insert into registrations_new (id, domain, did, secret, created, registered)
+			select id, domain, did, secret, created, registered from registrations;
+
+			drop table registrations;
+			alter table registrations_new rename to registrations;
+		`)
+		return err
+	})
+
 	// recreate and add rkey + created columns with default constraint
 	runMigration(db, "rework-collaborators-table", func(tx *sql.Tx) error {
 		// create new table

appview/db/registration.go

···
 	"encoding/hex"
 	"fmt"
 	"log"
+	"strings"
 	"time"
 )
 
+// Registration represents a knot registration. Knot would've been a better
+// name but we're stuck with this for historical reasons.
 type Registration struct {
 	Id         int64
 	Domain     string
···
 		where domain = ?;
 		`, domain)
 
+	return err
+}
+
+func AddKnot(e Execer, domain, did string) error {
+	_, err := e.Exec(`
+		insert into registrations (domain, did)
+		values (?, ?)
+	`, domain, did)
+	return err
+}
+
+func DeleteKnot(e Execer, filters ...filter) error {
+	var conditions []string
+	var args []any
+	for _, filter := range filters {
+		conditions = append(conditions, filter.Condition())
+		args = append(args, filter.Arg()...)
+	}
+
+	whereClause := ""
+	if conditions != nil {
+		whereClause = " where " + strings.Join(conditions, " and ")
+	}
+
+	query := fmt.Sprintf(`delete from registrations %s`, whereClause)
+
+	_, err := e.Exec(query, args...)
 	return err
 }