Bolting also allows the structure to be trued up after assembly, before everything is fully tightened down. I would suggest triangular gusset plates at each intersection, which can then also be drilled to take diagonal bracing in a couple of bays on each elevation. Since you are not going for a portal frame type of structure, you may also need to construct some kind of braced internal buttress frame at the halfway point of the wall to prevent it bulging or overturning when you get a roof structure in place.
Don't underestimate the power of the wind. Even in inland Europe, gusts can reach 90miles/hr and it is these that are the killers. Roofs are subject to suction as well as the force of the wind trapped inside through an open frontage. This is especially true of pitched roofs and a downwind section of a pitch is particularly seriously affected by this.
Have a look at this website selling steel building kits. It gives some ideas of how things are constructed.
https://www.steelbuildingsystems.co....BoC5KMQAvD_BwE