refactor: decompose Analyzer into recordPool and serviceAccumulator

Restructure the service analyzer architecture to improve maintainability:

- Extract recordPool (zone records + mark-delete claiming) and
  serviceAccumulator (service registry + domain normalization) as
  embedded structs in Analyzer
- Replace swap-delete with mark-delete to eliminate mutation-during-iteration
- Centralize domain normalization using helpers.DomainRelative
- Make Comment/NbResources lazy via Service.MarshalJSON instead of
  eager assignment at three separate call sites
- Extract SPF merging from usecase layer into services.CollectAndMergeSPF
- Add GetDefaultTTL accessor and comprehensive Analyzer doc comments
- Add round-trip test infrastructure covering MX, CNAME, CAA, TXT, SPF,
  DMARC, GSuite, Origin, Server and more

internal/usecase/zone/list_records.go

@@ -23,7 +23,6 @@ package zone
 
 import (
 	"fmt"
-	"strings"
 
 	"github.com/miekg/dns"
 
@@ -62,13 +61,6 @@ func (uc *ListRecordsUsecase) ToZoneFile(domain *happydns.Domain, zone *happydns
 func (uc *ListRecordsUsecase) List(domain *happydns.Domain, zone *happydns.Zone) (rrs []happydns.Record, err error) {
 	var svc_rrs []happydns.Record
 
-	// Collect SPF contributions keyed by absolute domain name.
-	type spfContrib struct {
-		directives [][]string
-		policies   []string
-	}
-	spfContribs := map[string]*spfContrib{}
-
 	for _, services := range zone.Services {
 		for _, svc := range services {
 			svc_rrs, err = uc.serviceListRecordsUC.List(svc, domain.DomainName, zone.DefaultTTL)
@@ -76,45 +68,6 @@ func (uc *ListRecordsUsecase) List(domain *happydns.Domain, zone *happydns.Zone)
 				return
 			}
 
-			// If the service is an SPF contributor, collect its directives
-			// and filter out any SPF TXT records it emits (they'll be
-			// replaced by the merged record).
-			if contributor, ok := svc.Service.(happydns.SPFContributor); ok {
-				directives := contributor.GetSPFDirectives()
-				policy := contributor.GetSPFAllPolicy()
-
-				// Compute the absolute domain for this service.
-				absDomain := svc.Domain
-				if domain.DomainName != "" {
-					if absDomain == "" {
-						absDomain = domain.DomainName
-					} else {
-						absDomain = absDomain + "." + domain.DomainName
-					}
-				}
-				if !strings.HasSuffix(absDomain, ".") {
-					absDomain += "."
-				}
-
-				if spfContribs[absDomain] == nil {
-					spfContribs[absDomain] = &spfContrib{}
-				}
-				spfContribs[absDomain].directives = append(spfContribs[absDomain].directives, directives)
-				if policy != "" {
-					spfContribs[absDomain].policies = append(spfContribs[absDomain].policies, policy)
-				}
-
-				// Drop SPF TXT records from this service's output.
-				filtered := svc_rrs[:0]
-				for _, rr := range svc_rrs {
-					if txt, ok := rr.(*happydns.TXT); ok && strings.HasPrefix(txt.Txt, "v=spf1") {
-						continue
-					}
-					filtered = append(filtered, rr)
-				}
-				svc_rrs = filtered
-			}
-
 			rrs = append(rrs, svc_rrs...)
 		}
 
@@ -127,28 +80,8 @@ func (uc *ListRecordsUsecase) List(domain *happydns.Domain, zone *happydns.Zone)
 		}
 	}
 
-	// Emit one merged SPF TXT record per domain that has SPF contributions.
-	for absDomain, contrib := range spfContribs {
-		merged := svcs.MergeSPFDirectives(contrib.directives...)
-		policy := svcs.ResolveSPFAllPolicy(contrib.policies)
-		merged = append(merged, policy)
-
-		spfFields := svcs.SPFFields{
-			Version:    1,
-			Directives: merged,
-		}
-
-		rr := &happydns.TXT{
-			Hdr: dns.RR_Header{
-				Name:   absDomain,
-				Rrtype: dns.TypeTXT,
-				Class:  dns.ClassINET,
-				Ttl:    zone.DefaultTTL,
-			},
-			Txt: spfFields.String(),
-		}
-		rrs = append(rrs, rr)
-	}
+	// Collect SPF contributions and merge into single records per domain.
+	rrs = svcs.CollectAndMergeSPF(domain.DomainName, zone, rrs, zone.DefaultTTL)
 
 	return
 }

internal/usecase/zone_service/add_to_zone.go

@@ -52,8 +52,6 @@ func (uc *AddToZoneUsecase) AddService(zone *happydns.Zone, subdomain happydns.S
 
 	service.Id = hash
 	service.Domain = string(subdomain)
-	service.NbResources = service.Service.GetNbResources()
-	service.Comment = service.Service.GenComment()
 
 	zone.Services[subdomain] = append(zone.Services[subdomain], service)