Magistrala (formerly Mainflux) IoT Platform SQL Injection via format Query Parameter

Magistrala (formerly Mainflux)'s message-readers API reads a `format` value from the HTTP query string (readers/api/http/transport.go) with no validation and interpolates it directly into raw SQL queries via fmt.Sprintf() in both the PostgreSQL reader (readers/postgres/messages.go: `fmt.Sprintf("SELECT * FROM %s WHERE %s ...", format, cond)`) and the TimescaleDB reader (readers/timescale/messages.go, same pattern), enabling SQL injection by any authenticated user able to query channel messages.