commonids: add commonid for TenantId

[catriona-m]

No description provided.

[tombuildsstuff]

LGTM 👍

[tombuildsstuff]

@manicminer given the default Tenant ID can be represented as / - do we also want a DefaultTenantID perhaps?

[manicminer]

Agreed, for convenience it might be worth declaring a default tenant for easy re-use. Otherwise LGTM 👍

var DefaultTenantId = TenantId{
	TenantId: "/",
}

[tombuildsstuff]

Thinking more about the default Tenant ID perhaps we want to handle this differently?

If we make the TenantId field a pointer, we could support parsing both the Default Tenant ID and another Tenant ID? It'd be different to the other Resource ID parsers but this is a unique case where the Default is handled differently, which I don't believe we've got anywhere else - so perhaps it's worth handling that explicitly here?

Suggested change

	// TenantId is a struct representing the Resource ID for a Tenant
	type TenantId struct {
	TenantId string
	}
	// DefaultTenantId returns a default TenantId
	var DefaultTenantId = NewTenantID("/")
	// NewTenantID returns a new TenantId struct
	func NewTenantID(tenantId string) TenantId {
	return TenantId{
	TenantId: tenantId,
	}
	}
	// TenantId is a struct representing the Resource ID for a Tenant
	type TenantId struct {
	TenantId *string
	}
	// NewDefaultTenantId returns a TenantId for the default Tenant
	func NewDefaultTenantID() TenantId {
	return TenantId{}
	}
	// NewTenantID returns a new TenantId struct
	func NewTenantID(tenantId string) TenantId {
	return TenantId{
	TenantId: &tenantId,
	}
	}

WDYT @catriona-m @manicminer?