new MOVR/GLMR operation: "account_transactions"

[spazcoin]

Description

• support new operation "account_transactions" for retrieving all transactions for an account. Structured so that I think support for filters and skipping can be added later.
• refactor moonbeam_scraper's "fetch_transactions" so that it can be used to retrieve transactions both for accounts and entire contract method (by pulling processor definition out).
• a little PEP8 cleanup and reStructured text docstrings for methods

Testing

• to make sure your "transactions" operation still works, I ran subscrape.py using your example config file and it chugged through Solarbeam transactions. Looks like about 7935 unique addresses, so hopefully that matches your previous results.

Future

• I'd suggest renaming your "transactions" operation to something like contract_transactions.
• I'd love to use your filtering module on moonriver/moonbeam, but it looks like you've only integrated it with ParachainScraper so far.

[spazcoin]

my scrape_config.json file is currently:

{
    "kusama": {
        "_skip": true,
        "extrinsics": {
            "_filter": [{"block_timestamp": [{"<":1644796800}]}],
            "system": [
                "remark"
            ]
        }
    },
    "moonriver": {
        "account_transactions": {
            "accounts": [
                "0xDEADBEEF"
            ],
            "_skip": false
        }
    }
}