Add DNS record data source

[Cyb3r-Jak3]

Adds a data source for an existing DNS record

Resolves #1904

[github-actions]

changelog detected ✅

[jacobbednarz]

i've added some notes inline; we probably need to work out how we want to search/filter for a single record before going any further.

[Cyb3r-Jak3]

For the search, what about using the list DNS record API call (https://api.cloudflare.com/#dns-records-for-a-zone-list-dns-records) but applying a filter of hostname and a type of "A" unless set? Could even make the page response only be 1 record on 1 page.

The only case where I can see that not working would be MX records, given they have a priority with likely the same hostname.

[jacobbednarz]

For the search, what about using the list DNS record API call (api.cloudflare.com/#dns-records-for-a-zone-list-dns-records) but applying a filter of hostname and a type of "A" unless set? Could even make the page response only be 1 record on 1 page.

yep, where possible, offload the actual searching the Cloudflare API and don't do it in the data source itself. check out cloudflare_zone for an example of this.

[Cyb3r-Jak3]

This is what I devised

records, err := client.DNSRecords(ctx, zoneID, searchRecord)
if err != nil {
	return diag.FromErr(fmt.Errorf("error listing DNS records: %w", err))
}

if len(records) == 0 {
	return diag.Errorf("didn't get any DNS records for hostname: %s", searchRecord.Name)
}

if len(records) != 1 && !contains([]string{"MX", "URI"}, searchRecord.Type) {
	return diag.Errorf("only wanted 1 DNS record. Got %d records", len(records))
} else {
	for _, record := range records {
		if record.Priority == searchRecord.Priority {
			records = []cloudflare.DNSRecord{record}
			break
		}
	}
	if len(records) != 1 {
		return diag.Errorf("unable to find single record for %s type %s", searchRecord.Name, searchRecord.Type)
	}
}

I can't do the page limiting as the cloudflare-go function only search with a DNS record and returns all matching records. The logic behind it is

1. Find all DNS records that have the same hostname and type. If no records found, throw an error.
2. If there is more than one record available, make sure that the type is either MX or URI (these are the only two with priority) or throw an error.
3. Search records to find one that match priority. If no records found then throw an error.

[github-actions]

This functionality has been released in v3.24.0 of the Terraform Cloudflare Provider.

Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!