Bump github.com/BurntSushi/toml from 0.3.1 to 0.4.1

Bumps [github.com/BurntSushi/toml](https://github.com/BurntSushi/toml) from 0.3.1 to 0.4.1.
- [Release notes](https://github.com/BurntSushi/toml/releases)
- [Commits](https://github.com/BurntSushi/toml/compare/v0.3.1...v0.4.1)

---
updated-dependencies:
- dependency-name: github.com/BurntSushi/toml
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/BurntSushi/toml/decode_meta.go

@@ -2,9 +2,9 @@ package toml
 
 import "strings"
 
-// MetaData allows access to meta information about TOML data that may not
-// be inferrable via reflection. In particular, whether a key has been defined
-// and the TOML type of a key.
+// MetaData allows access to meta information about TOML data that may not be
+// inferable via reflection. In particular, whether a key has been defined and
+// the TOML type of a key.
 type MetaData struct {
 	mapping map[string]interface{}
 	types   map[string]tomlType
@@ -13,10 +13,11 @@ type MetaData struct {
 	context Key // Used only during decoding.
 }
 
-// IsDefined returns true if the key given exists in the TOML data. The key
-// should be specified hierarchially. e.g.,
+// IsDefined reports if the key exists in the TOML data.
+//
+// The key should be specified hierarchically, for example to access the TOML
+// key "a.b.c" you would use:
 //
-//	// access the TOML key 'a.b.c'
 //	IsDefined("a", "b", "c")
 //
 // IsDefined will return false if an empty key given. Keys are case sensitive.
@@ -41,8 +42,8 @@ func (md *MetaData) IsDefined(key ...string) bool {
 
 // Type returns a string representation of the type of the key specified.
 //
-// Type will return the empty string if given an empty key or a key that
-// does not exist. Keys are case sensitive.
+// Type will return the empty string if given an empty key or a key that does
+// not exist. Keys are case sensitive.
 func (md *MetaData) Type(key ...string) string {
 	fullkey := strings.Join(key, ".")
 	if typ, ok := md.types[fullkey]; ok {
@@ -51,13 +52,11 @@ func (md *MetaData) Type(key ...string) string {
 	return ""
 }
 
-// Key is the type of any TOML key, including key groups. Use (MetaData).Keys
-// to get values of this type.
+// Key represents any TOML key, including key groups. Use (MetaData).Keys to get
+// values of this type.
 type Key []string
 
-func (k Key) String() string {
-	return strings.Join(k, ".")
-}
+func (k Key) String() string { return strings.Join(k, ".") }
 
 func (k Key) maybeQuotedAll() string {
 	var ss []string
@@ -68,6 +67,9 @@ func (k Key) maybeQuotedAll() string {
 }
 
 func (k Key) maybeQuoted(i int) string {
+	if k[i] == "" {
+		return `""`
+	}
 	quote := false
 	for _, c := range k[i] {
 		if !isBareKeyChar(c) {
@@ -76,7 +78,7 @@ func (k Key) maybeQuoted(i int) string {
 		}
 	}
 	if quote {
-		return "\"" + strings.Replace(k[i], "\"", "\\\"", -1) + "\""
+		return `"` + quotedReplacer.Replace(k[i]) + `"`
 	}
 	return k[i]
 }
@@ -89,10 +91,10 @@ func (k Key) add(piece string) Key {
 }
 
 // Keys returns a slice of every key in the TOML data, including key groups.
-// Each key is itself a slice, where the first element is the top of the
-// hierarchy and the last is the most specific.
 //
-// The list will have the same order as the keys appeared in the TOML data.
+// Each key is itself a slice, where the first element is the top of the
+// hierarchy and the last is the most specific. The list will have the same
+// order as the keys appeared in the TOML data.
 //
 // All keys returned are non-empty.
 func (md *MetaData) Keys() []Key {