A new config API is introduced, and ~all of the codebase is adapted to it.
The old API is kept but mainly only for dynamic usage where its extra flexibility is needed.
Using examples, the old config API looked this:
```
>>> config.get("request_expiry", 86400)
604800
>>> config.set_key("request_expiry", 86400)
>>>
```
The new config API instead:
```
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS
604800
>>> config.WALLET_PAYREQ_EXPIRY_SECONDS = 86400
>>>
```
The old API operated on arbitrary string keys, the new one uses
a static ~enum-like list of variables.
With the new API:
- there is a single centralised list of config variables, as opposed to
these being scattered all over
- no more duplication of default values (in the getters)
- there is now some (minimal for now) type-validation/conversion for
the config values
closes https://github.com/spesmilo/electrum/pull/5640
closes https://github.com/spesmilo/electrum/pull/5649
Note: there is yet a third API added here, for certain niche/abstract use-cases,
where we need a reference to the config variable itself.
It should only be used when needed:
```
>>> var = config.cv.WALLET_PAYREQ_EXPIRY_SECONDS
>>> var
<ConfigVarWithConfig key='request_expiry'>
>>> var.get()
604800
>>> var.set(3600)
>>> var.get_default_value()
86400
>>> var.is_set()
True
>>> var.is_modifiable()
True
```
- case 1: in version 4.4.1, 4.4.2, the qml GUI wizard allowed creating multisig wallets with an old_mpk as cosigner.
- case 2: in version 4.4.0, 4.4.1, 4.4.2, the qml GUI wizard allowed creating multisig wallets with mixed xpub/Ypub/Zpub.
The corresponding missing input validation was a bug in the wizard, it was unintended behaviour. Validation was added in d2cf21fc2b. Note however that there might be users who created such wallet files.
Re case 1 wallet files: there is no version of Electrum that allows spending from such a wallet. Coins received at addresses are not burned, however it is technically challenging to spend them. (unless the multisig can spend without needing the old_mpk cosigner in the quorum).
Re case 2 wallet files: it is possible to create a corresponding spending wallet for such a multisig, however it is a bit tricky. The script type for the addresses in such a heterogeneous xpub wallet is based on the xpub_type of the first keystore. So e.g. given a wallet file [Yprv1, Zpub2] it will have sh(wsh()) scripts, and the cosigner should create a wallet file [Ypub1, Zprv2] (same order).
Technically case 2 wallet files could be "fixed" automatically by converting the xpub types as part of a wallet_db upgrade. However if the wallet files also contain seeds, those cannot be converted ("standard" vs "segwit" electrum seed).
Case 1 wallet files are not possible to "fix" automatically as the cosigner using the old_mpk is not bip32 based.
It is unclear if there are *any* users out there affected by this. I suspect for case 1 it is very likely there are none (not many people have pre-2.0 electrum seeds which were never supported as part of a multisig who would also now try to create a multisig using them); for case 2 however there might be.
This commit breaks both case 1 and case 2 wallets: these wallet files can no longer be opened in new Electrum, an error message is shown and the crash reporter opens. If any potential users opt to send crash reports, at least we will know they exist and can help them recover.
The qt, qml, and kivy GUIs have a first-start network-setup screen
that allows the user customising the network settings before creating a wallet.
Previously the daemon used to create the network and start it, before this screen,
before the GUI even starts. If the user changed network settings, those would
be set on the already running network, potentially including restarting the network.
Now it becomes the responsibility of the GUI to start the network, allowing this
first-start customisation to take place before starting the network at all.
The qt and the qml GUIs are adapted to make use of this. Kivy, and the other
prototype GUIs are not adapted and just start the network right away, as before.
(this somehow escaped attention before, as most objects usually don't have multiple instances,
unless multiple wallets are open at the same time.)
Also, move all signal declarations, class constants and variables to the top of class definitions.
'last' property on WizardComponents is now queried from UI, not from the wizard.
This allows the content of the WizardComponent itself to be taken into account.
