Feature/transaction endpoint pt3 upsert

[brianium]

This adds support for replacing existing transaction records.

There is also an optional method flag that can be passed via json. If omitted, the default is append

To test against staging: http://bitkit-staging.0ce25c51.svc.dockerapp.io:8080

• [ ] POST to /transactions with method: append and see records added
• [ ] POST to /transactions with method: reset and check entire table is replaced
• [ ] POST to /transactions without a method and verify same as append behavior

Sample request payloads:

append

{
    "method": "append",
    "data": [
        {
            "txid": "testid-1",
            "fee_rate": 0.1234,
            "weight": 1
        },
        {
            "txid": "testid-2",
            "fee_rate": 0.2345,
            "weight": 2
        }
    ]
}

reset

{
    "method": "reset",
    "data": [
        {
            "txid": "testid-3",
            "fee_rate": 0.2345,
            "weight": 2
        }
    ]
}

upsert

{
    "method": "append",
    "data": [
        {
            "txid": "testid-3",
            "fee_rate": 0.2345,
            "weight": 7
        }
    ]
}

default

{
    "data": [
        {
            "txid": "testid-1",
            "fee_rate": 0.1234,
            "weight": 1
        },
        {
            "txid": "testid-2",
            "fee_rate": 0.2345,
            "weight": 2
        }
    ]
}