Creating a slack alert through API has issues with interpolating strings

Using this code in the explorer works but if creating a task through the API I get

```

[src/resetter.rs:61] &res.into_json().unwrap() = Object({
"code": String(
"invalid",
),
"message": String(
"failed to decode request: invalid character \'$\' after object key:value pair",
),
})

```

code:
```

import "slack"
import "influxdata/influxdb/monitor"

check = {
_check_id: "0000000000000001", // 16 characters, alphanumeric
_check_name: "Failed Tasks Check", // string
_type: "custom", // can also use "threashold" or "deadman"
tags: {},
}

url = "https://hooks.slack.com/services/adsadsaddsad"

from(bucket: "_tasks")
|> filter(fn: (r) => r["_measurement"] == "runs")
|> filter(fn: (r) => r["_field"] == "requestedAt")

|> pivot(
rowKey:["_time"],
columnKey: ["_field"],
valueColumn: "_value"
)

|> monitor.check(
crit: (r) => r.status == "success",
messageFn: (r) => "message",
data: check
)

|> map(fn: (r) => ({ status: slack.message(
url: url,
channel: "#test",
text: "\"${r.status}\" .",
color: "good"
)}))
|> yield(name: "mean")
```

Start with the API task-creation path and src/resetter.rs around line 61, then compare how the same Flux is handled in the explorer. Reproduce the request with the interpolated Slack message and trace the decoding error. Done means the API accepts and correctly processes the task without the invalid '$' character error.

Written by the indexing model from the issue text.