Line protocol parser's handling of missing tag value doesn't match 2.x behaviour

[trevorbonas]

Consider the following invalid line protocol:

readings,readings2,fleet=Alberta velocity=21.30 1577836800000000000

This point either has two measurement names or two tags, one with a value (fleet) and one without a value (readings2).

InfluxDB OSS 2.x interprets the issue with the point as the latter and gives the following error:

{
    "code": "invalid",
    "message": "unable to parse 'readings,readings2,fleet=Alberta velocity=21.30 1577836800000000000': missing tag value"
}

The influxdb_line_protocol crate does not return an error for this line protocol point. The parser interprets the first tag key as a part of the second tag key, producing the following ParsedLine struct:

ParsedLine {
    series: Series { 
        raw_input: "readings,readings2,fleet=Alberta",
        measurement: SingleSlice("readings"),
        tag_set: Some([(SingleSlice("readings2,fleet"), SingleSlice("Alberta"))])
    },
    field_set: [(SingleSlice("velocity"), F64(21.3))],
    timestamp: Some(1577836800000000000)
}