service: add csv.delim query param to load API

[nwt]

The csv.delim query parameter to the load API (POST /pool/{pool}/branch/{branch}) specifies the field delimiter for CSV input, allowing use of a character other than ",".

For #4238.

[philrz]

I just did a test on this branch at commit c085b95 with the same test data I used here to verify this worked with the CLI tooling, and it worked fine. Note that with this particular example of a semicolon I had to URL escape it.

$ wget "https://dgsaie.mise.gov.it/open_data_export.php?export-id=1&export-type=csvx"

$ curl http://localhost:9867/version
{"version":"v1.4.0-28-gc085b95a"}

$ zed create fuel
pool created: fuel 2KpLikYLBASDFXIinJO4dRD3TIg

$ curl -H "Content-Type: text/csv" --data-binary @open_data_export.php\?export-id\=1\&export-type\=csvx http://localhost:9867/pool/fuel/branch/main?csv.delim=%3B
{commit:0x105f14f2d02a46a39de465768fcc719c634db18f(=ksuid.KSUID),warnings:[]([string])}(=api.CommitResponse)

$ zed query -Z 'from fuel | head 1'
{
    "DATA_RILEVAZIONE": "2023-01-23",
    BENZINA: "1.829,47",
    GASOLIO_AUTO: "1.875,1",
    GPL: "797,85",
    GASOLIO_RISCALDAMENTO: "1.674,7",
    "O.C._FLUIDO_BTZ": "1.129,73",
    "O.C._DENSO_BTZ": "645,22"
}

So that's a functional 👍 for me!