Change default network to Regtest and default wallet db to Sqlite

[rajarshimaitra]

As discussed in #65 (comment) we might want to change the default network value to regtest instead of testnet.

Rationale: bdk-cli is mostly used in testing and demo purpose as an easy way to interact with BDK without write separate wallet codes. In such environment most of the testing I have found myself and others doing are on regtest. So it makes sense to make regtest the default option. And user can switch to testnet with -n flag. And mainnet is not allowed in bdk-cli anyway.

Update: I also feel having Sqlite as default db would move us towards same direction.. Sqlite makes it really easy to real time observe database updates in terminal as devs test out different scenarios..

Required changes: Mostly documentation updates to reflected the new cli usage. Code change is simple.

[rajarshimaitra]

I have added this under 0.6 milestone.. Would love to get this thing in before #92..

@notmandatory if there's concept ack on this, I can get this done quickly..

[notmandatory]

@rajarshimaitra If we make regtest the default network that means that users will also need at least the new regtest-bitcoin feature right? and that mean's we'd need to include that feature in the default feature set? I'm trying to image what a user who is just doing a cargo install bdk-cli would expect. Concept ACK as long as you're also planning to add regtest-bitcoin to the default features, otherwise we should discuss more.

[rajarshimaitra]

If we make regtest the default network that means that users will also need at least the new regtest-bitcoin feature right?

I don't think that's the case.. They can run regtest just like they are running testnet right now.. By running a regtest backend node and connecting to the rpc port (which mostly works by default).. They don't need regtest-bitcoin to run it.. Thats only when they want the automated node feature..

As a user its easier for me to expect bdk-cli wallet <command> to just connect to my running regtest node without specifying anything else.. But thats mostly because I run my tests in regtests more than in testnets.. That was basically the motivation of this change..

But I have also observed most of the time the default testnet network also works fine with regtest node too.. And that's probably because the address formats for both of them are same.. But then they need to specify rpc port correctly..

My initial thought was, as bdk-cli is mostly used as a dev and testing ground, maybe it makes sense to connect to regtest with as minimal config possible..

Having sqlite by default is actually more useful.. Which is already done in #99 ..

But its also a good question if we should add regtest-bitcoin as default too.. I am not sure on that, but could a very wholesome experience for anyone running cargo install bdk-cli in that case.. They can just start doing wallet ops from get go, without needing to setup anything else.. And in that case we do need to make regtest default network..
I am open for suggestions here..

[rajarshimaitra]

closing in favor of #109 and we can carry on the discussion there on general default value set..