docs: update provider docs for full CRUD support

docs/resources/dns_record.md

@@ -0,0 +1,104 @@
+# dynu_dns_record Resource
+
+Manages a Dynu DNS record under the Dynu root domain resolved from `hostname`.
+
+## Example Usage
+
+### A record
+
+```terraform
+resource "dynu_dns_record" "a" {
+  hostname    = "www.example.com"
+  record_type = "A"
+  content     = "198.51.100.20"
+  ttl         = 300
+}
+```
+
+### CNAME record
+
+```terraform
+resource "dynu_dns_record" "cname" {
+  hostname    = "app.example.com"
+  record_type = "CNAME"
+  content     = "target.example.net"
+}
+```
+
+### MX record
+
+```terraform
+resource "dynu_dns_record" "mx" {
+  hostname    = "example.com"
+  record_type = "MX"
+  content     = "mail.example.com"
+  priority    = 10
+}
+```
+
+### TXT record
+
+```terraform
+resource "dynu_dns_record" "txt" {
+  hostname    = "example.com"
+  record_type = "TXT"
+  content     = "v=spf1 include:_spf.example.com ~all"
+}
+```
+
+### SRV record
+
+```terraform
+resource "dynu_dns_record" "srv" {
+  hostname    = "_sip._tcp.example.com"
+  record_type = "SRV"
+  content     = "sip.example.com"
+  priority    = 10
+  weight      = 5
+  port        = 5060
+}
+```
+
+## Schema
+
+### Required
+
+- `hostname` (String) Fully-qualified hostname.
+- `record_type` (String) DNS record type.
+
+### Optional + Computed
+
+- `content` (String)
+- `dynamic` (Boolean)
+- `ttl` (Number)
+- `enabled` (Boolean, defaults to `true`)
+- `group` (String)
+- `host` (String)
+- `priority` (Number)
+- `weight` (Number)
+- `port` (Number)
+- `flags` (Number)
+- `tag` (String)
+- `value` (String)
+- `node_name` (String)
+
+Type-specific notes:
+- `A`/`AAAA` support dynamic semantics using omitted `content` or explicit `dynamic = true`.
+- `MX` and `SRV` use `priority`.
+- `SRV` also uses `weight` and `port`.
+- `CAA` uses `flags`, `tag`, and `value`.
+
+### Computed
+
+- `id` (String) Composite ID in `domain_id/record_id` format.
+- `domain_id` (Number)
+- `domain_name` (String)
+- `updated_on` (String)
+
+## Import
+
+Import using `domain_id/record_id`:
+
+```bash
+terraform import dynu_dns_record.example 1234/5678
+```