Try to mine a block in the zcash testnet

[oxarbitrage]

Here we want to discuss and propose ideas to create shorter term goal for the getblocktemplate work in order to somehow "mine" a block in the testnet.

What gets proposed here should be added to #5803

[teor2345]

I think we can do testing using a block proposal, which is a block without a proof of work.

Here's how we could do that:

1. Finish all the required getblocktemplate RPC fields
2. Create a block header from the RPC fields, with a zeroed-out equihash solution, and serialize it
3. Create the block transactions by combining all the coinbasetxn and transaction data fields
4. Send that block to zcashd using `getblocktemplate '{ "mode": "proposal", "data": "(hex data)" }'

zcashd has proposal support, but it's not documented. Here's the spec:
https://en.bitcoin.it/wiki/BIP_0023#Block_Proposal

[oxarbitrage]

Thanks @teor2345 that looks good.

@arya2 do you have any additional comments to what Teor is proposing ? I want to add that to the details section of #5803

[arya2]

Nope, that plan looks good.

[mpguerra]

Any other potential ideas to discuss? Should be consider this discussion closed?