Updated metric alert to include integration id for slack action

[GirtsZemitis]

Currently, it seems that it's not possible to use slack action for metric alerts. If defining action like this

type               = "slack"
target_type        = "specific"
target_identifier  = "#chanel-name"

We get error > {"integration":["Integration must be provided for slack"]}

I am not great in go but tried to make a small proof of concept PR for what would need to be added to make it possibly work. Hopefully, you can fix and extend this to make slack actions also supported.

[taj-p]

Sorry!

I am not great in go but tried to make a small proof of concept PR for what would need to be added to make it possibly work. Hopefully, you can fix and extend this to make slack actions also supported.

I just read this! I've piggybacked off this great starter and created another PR here: https://github.com/jianyuan/terraform-provider-sentry/pull/217

Note that we also have to update the go-sentry dependency to take in a list of scopes as opposed to a *string (PR: https://github.com/jianyuan/go-sentry/pull/66)

[jianyuan]

Continued in https://github.com/jianyuan/terraform-provider-sentry/pull/217