Better Electrum and Esplora clients

[thunderbiscuit]

Our Electrum and Esplora clients are not offering all that's available to standard Electrum and Esplora clients. Many of the available methods are not useful at the bdk-ffi layer (things like subscribing to specific script updates), but some could be (like requesting a particular block header, or requesting a random transaction given its Txid).

After looking at the APIs for Electrum and Esplora, here are a few I think could be useful for folks interacting with these clients.

Electrum

• ElectrumApi::block_header()
• ElectrumApi::relay_fee()
• ElectrumApi::transaction_get_raw() or ElectrumApi::transaction_get()
• ElectrumApi::ping()

Esplora

• BlockingClient::get_tx()
• BlockingClient::get_tx_status()
• BlockingClient::get_tx_info()
• BlockingClient::get_block_by_hash()

[reez]

Electrum

ElectrumApi::block_headers_subscribe()

Esplora

BlockingClient::get_block_hash()

• PR Add get_block_hash to esplora #665

Per discussion w Conor

[ConorOkus]

bitcoindevkit/bdk#603

[reez]

Esplora

• BlockingClient::get_tx()

We've got get_tx() https://github.com/bitcoindevkit/bdk-ffi/blob/master/bdk-ffi/src/esplora.rs#L87 so I think we can cross that one off

[andreasgriffin]

Please also include

• proxy in electrum: https://docs.rs/electrum-client/0.23.0/electrum_client/struct.ConfigBuilder.html
• proxy in esplora: https://docs.rs/esplora-client/0.11.0/esplora_client/struct.Builder.html#method.proxy

[reez]

Please also include

• proxy in electrum: https://docs.rs/electrum-client/0.23.0/electrum_client/struct.ConfigBuilder.html
• proxy in esplora: https://docs.rs/esplora-client/0.11.0/esplora_client/struct.Builder.html#method.proxy

This part is resolved by #711 now

[thunderbiscuit]

@ItoroD I'll assign you to this one as discussed! Not all APIs need to be added, I just want someone to take another look and see if we can bring them easily, or outline where things might get tricky.