bump to v0.2.0: complete provider implementation with live-tested DNS record types

- DYNU_API_KEY env var fallback in provider config
- dynu_domain resource: add 9 computed attributes (unicode_name, ipv4/ipv6 flags,
  wildcard aliases, allow_zone_transfer, dnssec, created_on, updated_on)
- dynu_dns_records data source: add 6 type-specific fields (priority, weight,
  port, flags, tag, value)
- Fix normalizeRecordContentForState for MX/SRV/NS/PTR (read host field) and CAA
  (read value field) to avoid plan/state inconsistency
- Allow underscore-prefixed DNS labels in hostname validator (RFC 2782 SRV)
- Preserve plan/state hostname across create/update/read to prevent inconsistent
  result errors when API returns full FQDN for node_name-style records
- Update all version references from 0.1.0 to 0.2.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LFZyrmtKsezBwFWGTWsb2y

internal/provider/provider.go

@@ -2,6 +2,7 @@ package provider
 
 import (
 	"context"
+	"os"
 	"strings"
 
 	"github.com/hashicorp/terraform-plugin-framework/datasource"
@@ -47,7 +48,7 @@ func (p *dynuProvider) Schema(_ context.Context, _ provider.SchemaRequest, resp
 			"api_key": schema.StringAttribute{
 				Optional:    true,
 				Sensitive:   true,
-				Description: "Dynu API key. Set this explicitly, such as via a Terraform variable in terraform.tfvars.",
+				Description: "Dynu API key. Can also be set via the DYNU_API_KEY environment variable.",
 			},
 			"base_url": schema.StringAttribute{
 				Optional:    true,
@@ -82,9 +83,11 @@ func (p *dynuProvider) Configure(ctx context.Context, req provider.ConfigureRequ
 
 func resolveAPIKey(configValue types.String) string {
 	if !configValue.IsNull() && !configValue.IsUnknown() {
-		return strings.TrimSpace(configValue.ValueString())
+		if v := strings.TrimSpace(configValue.ValueString()); v != "" {
+			return v
+		}
 	}
-	return ""
+	return strings.TrimSpace(os.Getenv("DYNU_API_KEY"))
 }
 
 func (p *dynuProvider) DataSources(_ context.Context) []func() datasource.DataSource {