* Progress towards mock MainPod verification
* add MockMainPod.pub_statements logic so that when originid==SELF it is replaced by self.id()
* Basic op checking for mock MainPOD
* More op checking
* Add TODO notes
---------
Co-authored-by: arnaucube <git@arnaucube.com>
Migrate fmt to use Display trait to simplify the usage of it.
Also with this, in the same snipped of code we can print types from
backend, middleware and frontend; which before needed to import the two
different `Printer` structs (frontend::Printer and mock_main::Printer).
Before:
```
let printer = mock_main::Printer { skip_none: false };
let mut w = io::stdout();
printer.fmt_mock_main_pod(&mut w, &pod).unwrap();
let printer = frontend::Printer { skip_none: false };
printer.fmt_main_pod_builder(&mut w, &pod_builder).unwrap();
```
now:
```
println!("{:#}", pod);
println!("{:#}", pod_builder);
```
And the equivalent to the old `skip_none: true`, now is done by just
using `println!("{}", pod);
* compute MainPod.id from pub_statements; and introduce the trait `ToFields`
Compute MainPod.id from pub_statements hash; for it, introduce the trait
`ToFields` at the middleware and implement it for the Statement related
types.
* cleaner statements tofield iter
Co-authored-by: Ahmad Afuni <root@ahmadafuni.com>
---------
Co-authored-by: Ahmad Afuni <root@ahmadafuni.com>
