Update Linode API to v4

Linode API has made breaking changes that are resolved by this
update. No user action is required.

Additionally, related README.md entry updated to include new cloud
manager interface.

dnsapi/README.md

@@ -264,9 +264,18 @@ when needed.
 ## 14. Use Linode domain API
 
 First you need to login to your Linode account to get your API Key.
-[https://manager.linode.com/profile/api](https://manager.linode.com/profile/api)
 
-Then add an API key with label *ACME* and copy the new key.
+  * [Classic Manager](https://manager.linode.com/profile/api)
+
+   Under "Add an API key", Give the new key a "Label" (we recommend *ACME*),
+   set the expiry to never, "Create API Key", and copy the new key into the `LINODE_API_KEY` command
+   below.
+
+  * [Cloud Manager](https://cloud.linode.com/profile/tokens)
+
+   Click on "Add a Personal Access Token". Give the new key a "Label" (we
+   recommend *ACME*), give it Read/Write access to "Domains". "Submit", and
+   copy the new key into the `LINODE_API_KEY` command below.
 
 ```sh
 export LINODE_API_KEY="..."

dnsapi/dns_linode.sh

@@ -2,7 +2,7 @@
 
 #Author: Philipp Grosswiler <philipp.grosswiler@swiss-design.net>
 
-LINODE_API_URL="https://api.linode.com/?api_key=$LINODE_API_KEY&api_action="
+LINODE_API_URL="https://api.linode.com/v4/domains"
 
 ########  Public functions #####################
 
@@ -27,10 +27,14 @@ dns_linode_add() {
   _debug _sub_domain "$_sub_domain"
   _debug _domain "$_domain"
 
-  _parameters="&DomainID=$_domain_id&Type=TXT&Name=$_sub_domain&Target=$txtvalue"
+  _payload="{
+              \"type\": \"TXT\",
+              \"name\": \"$_sub_domain\",
+              \"target\": \"$txtvalue\"
+            }"
 
-  if _rest GET "domain.resource.create" "$_parameters" && [ -n "$response" ]; then
-    _resource_id=$(printf "%s\n" "$response" | _egrep_o "\"ResourceID\":\s*[0-9]+" | cut -d : -f 2 | tr -d " " | _head_n 1)
+  if _rest POST "/$_domain_id/records" "$_payload" && [ -n "$response" ]; then
+    _resource_id=$(printf "%s\n" "$response" | _egrep_o "\"id\":\s*[0-9]+" | cut -d : -f 2 | tr -d " " | _head_n 1)
     _debug _resource_id "$_resource_id"
 
     if [ -z "$_resource_id" ]; then
@@ -65,25 +69,21 @@ dns_linode_rm() {
   _debug _sub_domain "$_sub_domain"
   _debug _domain "$_domain"
 
-  _parameters="&DomainID=$_domain_id"
-
-  if _rest GET "domain.resource.list" "$_parameters" && [ -n "$response" ]; then
+  if _rest GET "/$_domain_id/records" && [ -n "$response" ]; then
     response="$(echo "$response" | tr -d "\n" | tr '{' "|" | sed 's/|/&{/g' | tr "|" "\n")"
 
-    resource="$(echo "$response" | _egrep_o "{.*\"NAME\":\s*\"$_sub_domain\".*}")"
+    resource="$(echo "$response" | _egrep_o "{.*\"name\":\s*\"$_sub_domain\".*}")"
     if [ "$resource" ]; then
-      _resource_id=$(printf "%s\n" "$resource" | _egrep_o "\"RESOURCEID\":\s*[0-9]+" | _head_n 1 | cut -d : -f 2 | tr -d \ )
+      _resource_id=$(printf "%s\n" "$resource" | _egrep_o "\"id\":\s*[0-9]+" | _head_n 1 | cut -d : -f 2 | tr -d \ )
       if [ "$_resource_id" ]; then
         _debug _resource_id "$_resource_id"
 
-        _parameters="&DomainID=$_domain_id&ResourceID=$_resource_id"
-
-        if _rest GET "domain.resource.delete" "$_parameters" && [ -n "$response" ]; then
-          _resource_id=$(printf "%s\n" "$response" | _egrep_o "\"ResourceID\":\s*[0-9]+" | cut -d : -f 2 | tr -d " " | _head_n 1)
-          _debug _resource_id "$_resource_id"
+        if _rest DELETE "/$_domain_id/records/$_resource_id" && [ -n "$response" ]; then
+          # On 200/OK, empty set is returned. Check for error, if any.
+          _error_response=$(printf "%s\n" "$response" | _egrep_o "\"errors\"" | cut -d : -f 2 | tr -d " " | _head_n 1)
 
-          if [ -z "$_resource_id" ]; then
-            _err "Error deleting the domain resource."
+          if [ -n "$_error_response" ]; then
+            _err "Error deleting the domain resource: $_error_response"
             return 1
           fi
 
@@ -127,7 +127,7 @@ _get_root() {
   i=2
   p=1
 
-  if _rest GET "domain.list"; then
+  if _rest GET; then
     response="$(echo "$response" | tr -d "\n" | tr '{' "|" | sed 's/|/&{/g' | tr "|" "\n")"
     while true; do
       h=$(printf "%s" "$domain" | cut -d . -f $i-100)
@@ -137,9 +137,9 @@ _get_root() {
         return 1
       fi
 
-      hostedzone="$(echo "$response" | _egrep_o "{.*\"DOMAIN\":\s*\"$h\".*}")"
+      hostedzone="$(echo "$response" | _egrep_o "{.*\"domain\":\s*\"$h\".*}")"
       if [ "$hostedzone" ]; then
-        _domain_id=$(printf "%s\n" "$hostedzone" | _egrep_o "\"DOMAINID\":\s*[0-9]+" | _head_n 1 | cut -d : -f 2 | tr -d \ )
+        _domain_id=$(printf "%s\n" "$hostedzone" | _egrep_o "\"id\":\s*[0-9]+" | _head_n 1 | cut -d : -f 2 | tr -d \ )
         if [ "$_domain_id" ]; then
           _sub_domain=$(printf "%s" "$domain" | cut -d . -f 1-$p)
           _domain=$h
@@ -165,6 +165,7 @@ _rest() {
 
   export _H1="Accept: application/json"
   export _H2="Content-Type: application/json"
+  export _H3="Authorization: Bearer $LINODE_API_KEY"
 
   if [ "$mtd" != "GET" ]; then
     # both POST and DELETE.