Use caddy's certmagic library for extensible/robust ACME handling (#14177)

* use certmagic for more extensible/robust ACME cert handling

* accept TOS based on config option

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/libdns/libdns/libdns.go

@@ -0,0 +1,85 @@
+// Package libdns defines the core interfaces that should be implemented
+// by DNS provider clients. They are small and idiomatic Go interfaces with
+// well-defined semantics.
+//
+// All interface implementations must be safe for concurrent/parallel use.
+// For example, if AppendRecords() is called at the same time and two API
+// requests are made to the provider at the same time, the result of both
+// requests must be visible after they both complete; if the provider does
+// not synchronize the writing of the zone file and one request overwrites
+// the other, then the client implementation must take care to synchronize
+// on behalf of the incompetent provider. This synchronization need not be
+// global, for example: the scope of synchronization might only need to be
+// within the same zone, allowing multiple requests at once as long as all
+// of them are for different zones. (Exact logic depends on the provider.)
+package libdns
+
+import (
+	"context"
+	"time"
+)
+
+// RecordGetter can get records from a DNS zone.
+type RecordGetter interface {
+	// GetRecords returns all the records in the DNS zone.
+	//
+	// Implementations must honor context cancellation and be safe for
+	// concurrent use.
+	GetRecords(ctx context.Context, zone string) ([]Record, error)
+}
+
+// RecordAppender can non-destructively add new records to a DNS zone.
+type RecordAppender interface {
+	// AppendRecords creates the requested records in the given zone
+	// and returns the populated records that were created. It never
+	// changes existing records.
+	//
+	// Implementations must honor context cancellation and be safe for
+	// concurrent use.
+	AppendRecords(ctx context.Context, zone string, recs []Record) ([]Record, error)
+}
+
+// RecordSetter can set new or update existing records in a DNS zone.
+type RecordSetter interface {
+	// SetRecords updates the zone so that the records described in the
+	// input are reflected in the output. It may create or overwrite
+	// records or -- depending on the record type -- delete records to
+	// maintain parity with the input. No other records are affected.
+	// It returns the records which were set.
+	//
+	// Records that have an ID associating it with a particular resource
+	// on the provider will be directly replaced. If no ID is given, this
+	// method may use what information is given to do lookups and will
+	// ensure that only necessary changes are made to the zone.
+	//
+	// Implementations must honor context cancellation and be safe for
+	// concurrent use.
+	SetRecords(ctx context.Context, zone string, recs []Record) ([]Record, error)
+}
+
+// RecordDeleter can delete records from a DNS zone.
+type RecordDeleter interface {
+	// DeleteRecords deletes the given records from the zone if they exist.
+	// It returns the records that were deleted.
+	//
+	// Records that have an ID to associate it with a particular resource on
+	// the provider will be directly deleted. If no ID is given, this method
+	// may use what information is given to do lookups and delete only
+	// matching records.
+	//
+	// Implementations must honor context cancellation and be safe for
+	// concurrent use.
+	DeleteRecords(ctx context.Context, zone string, recs []Record) ([]Record, error)
+}
+
+// Record is a generalized representation of a DNS record.
+type Record struct {
+	// provider-specific metadata
+	ID string
+
+	// general record fields
+	Type  string
+	Name  string
+	Value string
+	TTL   time.Duration
+}