Make payjoin-cli v1 / v2 features additive (payjoin#538)

Fix payjoin#500 

Following @nothingmuch's suggestion:

> 1. make appconfig more hierarchical, and support both v1 and v2
specific options in sub-structures, that are not feature gated. also
move bitcoind related stuff to its own substructure
>
> 2. out of appconfig, generate helper stuff, again i was focused on a
struct representing bitcoind (or more generally wallet) capabilities for
payjoin, to avoid needing to impl the `bitcoind` method in the trait
impls and to hide the details (e.g. error checking, psbt parsing, etc)
from the actual App impls, optimizing readability to correspond high
level description of the spec
>
> 3. adding an explicit --prefer-bip-78 or option, or something similar,
for payjoin-cli compiled with both. due to the backwards compatibility
of bip77 that probably requires more than one flag or something that is
not just boolean valued, e.g. as a sender be able to send bip78 only
even to a bip77 receiver and even if v2 support is compiled can be
useful for e2e testing with a single build
>

I think we're much closer to @nothingmuch's goal:

> my goal was making sure both app/v{1,2}.rs kind of give a high level
overview of both the protocol and the code, de-emphasizing the details
like how to talk to bitcoind and emphasizing its role as a reference
implementation for bip 77 specifically.

Perhaps some network details could still be abstracted away to make this
even more clear. But in terms of repaying tech debt and fixing the devex
by making features additive, this should be complete.

Author: spacebear21

payjoin-cli/contrib/test.sh

@@ -1,5 +1,4 @@
 #!/usr/bin/env bash
 set -e
 
-cargo test --locked --package payjoin-cli --verbose --no-default-features --features=_danger-local-https,v2 --test e2e
-cargo test --locked --package payjoin-cli --verbose --no-default-features --features=v1,_danger-local-https
+cargo test --locked --package payjoin-cli --verbose --all-features

payjoin-cli/example.config.toml

@@ -2,18 +2,25 @@
 ## Payjoin config.toml configuration file. Lines beginning with # are comments.
 ##
 
-# Bitcoin RPC Connection Settings
-# ------------------------------
+# Common Settings
+# --------------
+
+# The path to the database file
+db_path = "payjoin.db"
 
+# The maximum fee rate that the receiver is willing to pay (in sat/vB)
+max_fee_rate = 2.0
 
+# Bitcoin RPC Connection Settings
+# ------------------------------
+[bitcoind]
 # The RPC host of the wallet to connect to.
 # For example, if the wallet is "sender", then default values are:
 # 	- mainnet: http://localhost:8332/wallet/sender
 # 	- testnet: http://localhost:18332/wallet/sender
 # 	- regtest: http://localhost:18443/wallet/sender
 # 	- signet: http://localhost:38332/wallet/sender
-bitcoind_rpchost="http://localhost:18443/wallet/sender"
-
+rpchost = "http://localhost:18443/wallet/sender"
 
 # The RPC .cookie file used only for local authentication to bitcoind.
 # If rpcuser and rpcpassword are being used, this is not necessary.
@@ -22,36 +29,28 @@ bitcoind_rpchost="http://localhost:18443/wallet/sender"
 # 	MacOS: ~/Library/Application Support/Bitcoin/<NETWORK>/.cookie
 # 	Windows Vista and later: C:\Users\YourUserName\AppData\Roaming\Bitcoin\<NETWORK>\.cookie
 # 	Windows XP: C:\Documents and Settings\YourUserName\Application Data\Bitcoin\<NETWORK>\.cookie
-# bitcoind_cookie=
-
+cookie = ""
 
 # The rpcuser to connect to (specified in bitcoin.conf).
-bitcoind_rpcuser="user"
-
+rpcuser = "user"
 
 # The rpcpassword of the user to connect to (specified in bitcoin.conf).
-bitcoind_rpcpassword="password"
-
-## Payjoin Settings
-## ----------------
-
-
-# (v1, receiver only) The port for v1 receiving servers to bind to.
-port="3000"
-
-
-# (v1, receiver only) The payjoin endpoint which coordinates the transaction.
-pj_endpoint="https://localhost:3000"
-
-
-# (v2 only) The payjoin directory to rendezvous at.
-pj_directory = "https://payjo.in"
-
-
-# (v2 only) The OHTTP relay that will forward requests to the OHTTP Gateway, which will forward to the pj_endpoint directory.
-ohttp_relay="https://pj.bobspacebkk.com"
-
-
-# (v2 only, optional) The HPKE keys which need to be fetched ahead of time from the pj_endpoint for the payjoin packets to be encrypted.
-# These can now be fetched and no longer need to be configured.
-ohttp_keys="./path/to/ohttp_keys"
+rpcpassword = "password"
+
+# Version Configuration
+# -------------------
+# Uncomment ONE of the following version configurations depending on which version you want to use
+
+# Version 1 Configuration
+# [v1]
+# port = 3000
+# pj_endpoint = "https://localhost:3000"
+
+# Version 2 Configuration
+# [v2]
+# pj_directory = "https://payjo.in"
+# ohttp_relay = "https://pj.bobspacebkk.com"
+# # Optional: The HPKE keys which need to be fetched ahead of time from the pj_endpoint
+# # for the payjoin packets to be encrypted.
+# # These can now be fetched and no longer need to be configured.
+# ohttp_keys = "./path/to/ohttp_keys"