Recently we (*cough* Tobin) made the `Map` trait private and neglected
to add a public API for combining together two PSBTs. Doing so broke the
`psbt` module.
Pull the merge logic out of the `Map` trait and put it in methods on
each individual type (`Input`, `Output`, `PartiallySignedTransaction`).
Doing so allows for simplification of return types since combining
inputs/outputs never errors.
Use the term 'combine' instead of 'merge' since that is the term used in
BIP 174.
Rust idiomatic style is to put the rustdoc _above_ any attributes on
types, functions, etc.
Audit the codebase and move comments/attributes to the correct place.
Add a trailing full stop at times to neaten things up a little extra.
Based on the original work by Justin Moon.
*MSRV unchanged from 1.29.0.*
When `std` is off, `no-std` must be on, and we use the [`alloc`](https://doc.rust-lang.org/alloc/) and core2 crates. The `alloc` crate requires the user define a global allocator.
* Import from `core` and `alloc` instead of `std`
* `alloc` only used if `no-std` is on
* Create `std` feature
* Create `no-std` feature which adds a core2 dependency to polyfill `std::io` features. This is an experimental feature and should be
used with caution.
* CI runs tests `no-std`
* MSRV for `no-std` is 1.51 or so
Tobin Harding
Dr Maxim Orlovsky
Devrandom
Sebastian
Riccardo Casatta
sanket1729
Elichai Turkel
Andrew Poelstra
Carl Dong