CLOUDFLAREAPI: Adds CF_WORKER_ROUTE (#1243)

* CLOUDFLAREAPI: Adds CF_WORKER_ROUTE.

- CLOUDFLAREAPI: Initial support for CF_WORKER_ROUTE.
- Put CF_WORKER_ROUTE behind a per-domain feature-flag.
- Adds Integration Test.
- Create Cloudflare workers for tests.
- Updates documentation.

* Workaround for updateWorkerRoute causing stack overflow.

* Sets AccountID.

* Updates to latest master (Thanks @tresni!).

* Removes $CLOUDFLAREAPI_ACCOUNTNAME.

* Add alltrue() filter and -cfworkers flag

* Final workers changes

* alltrue() should be implemented like other filters.
* Update documentation.

Co-authored-by: Tom Limoncelli <tlimoncelli@stackoverflow.com>

docs/_functions/domain/CF_WORKER_ROUTE.md

@@ -0,0 +1,29 @@
+---
+name: CF_WORKER_ROUTE
+parameters:
+  - pattern
+  - script
+---
+
+`CF_WORKER_ROUTE` uses the [Cloudflare Workers](https://developers.cloudflare.com/workers/) 
+API to manage [worker routes](https://developers.cloudflare.com/workers/platform/routes)
+for a given domain.
+
+If _any_ `CF_WORKER_ROUTE` function is used then `dnscontrol` will manage _all_ 
+Worker Routes for the domain. To be clear: this means it will delete existing routes that
+were created outside of DNSControl.
+
+WARNING: This interface is not extensively tested. Take precautions such as making
+backups and manually verifying `dnscontrol preview` output before running
+`dnscontrol push`.
+
+This example assigns the patterns `api.foo.com/*` and `foo.com/api/*` to a `my-worker` script:
+
+{% include startExample.html %}
+{% highlight js %}
+D("foo.com", .... ,
+    CF_WORKER_ROUTE("api.foo.com/*", "my-worker"),
+    CF_WORKER_ROUTE("foo.com/api/*", "my-worker"),
+);
+{%endhighlight%}
+{% include endExample.html %}