DOCS: Add tips about TXT records (#1622)

* Add tips about TXT records

* More comments

* Remove test temporarily

* go generate

* A a link to the test

models/t_parse.go

@@ -5,13 +5,33 @@ import (
 	"net"
 )
 
-// PopulateFromString populates a RecordConfig given a type and string.
-// Many providers give all the parameters of a resource record in one big
-// string (all the parameters of an MX, SRV, CAA, etc). Rather than have
-// each provider rewrite this code many times, here's a helper function to use.
+// PopulateFromString populates a RecordConfig given a type and string.  Many
+// providers give all the parameters of a resource record in one big string.
+// This helper function lets you not re-invent the wheel.
+//
+// NOTE: You almost always want to special-case TXT records. Every provider
+// seems to quote them differently.
+//
+// Recommended calling convention:  Process the exceptions first, then use the
+// function for everything else.
+//	  var err error
+//	  switch rType {
+//    case "MX":
+//        // MX priority in a separate field.
+//        if err := rc.SetTargetMX(cr.Priority, target); err != nil {
+//          return nil, fmt.Errorf("unparsable MX record received from cloudflare: %w", err)
+//        }
+//	  case "TXT":
+//        // TXT records are stored verbatim; no quoting/escaping to parse.
+//		  err = rc.SetTargetTXT(target)
+//        // ProTip: Use rc.SetTargetTXTs(manystrings) if the API or parser returns a list of substrings.
+//	  default:
+//		  err = rec.PopulateFromString(rType, target, origin)
+//	  }
+//	  if err != nil {
+//		  return nil, fmt.Errorf("unparsable record received from CHANGE_TO_PROVDER_NAME: %w", err)
+//	  }
 //
-// If this doesn't work for all rtypes, process the special cases then
-// call this for the remainder.
 func (rc *RecordConfig) PopulateFromString(rtype, contents, origin string) error {
 	if rc.Type != "" && rc.Type != rtype {
 		panic(fmt.Errorf("assertion failed: rtype already set (%s) (%s)", rtype, rc.Type))