📜 update readme

functions/README.md

@@ -10,6 +10,8 @@ Pages Functions are very similar to Cloudflare Workers; however they will always
 Pages Functions use file-based routing, which means that the file `grapher/[slug].ts` will serve routes like `/grapher/child-mortality`.
 In addition, there's a [`_routes.json`](../_routes.json) file that specifies which routes are to be served dynamically.
 
+Inside a file-based route we sometimes use an instance of itty-router to decide on the exact functionality to provide (e.g. png vs svg generation)
+
 ## Development
 
 1. Copy `.dev.vars.example` to `.dev.vars` and fill in the required variables.
@@ -28,15 +30,17 @@ Note: compatibility dates between local development, production and preview envi
 
 ## Testing on Fondation staging sites vs Cloudfare previews
 
-`yarn deployContentPreview` deploys the staging `bakedSite` to a Cloudflare preview at https://[PREVIEW_BRANCH].owid-staging.pages.dev. This is the recommended way to test functions in a production-like environment. See [../ops/buildkite/deploy-content-preview](../ops/buildkite/deploy-content-preview) for more details.
+We have two cloudflare projects set up that you can deploy previews to. `owid` which is also where our production deployment runs, and `owid-staging`. Currently, `owid` is configured to require authentication while `owid-staging` is accessible from the internet without any kind of auth.
+
+`yarn deployContentPreview` deploys the staging `bakedSite` to a Cloudflare preview at https://[PREVIEW_BRANCH].[PROJECT].pages.dev. This is the recommended way to test functions in a production-like environment. See [../ops/buildkite/deploy-content-preview](../ops/buildkite/deploy-content-preview) for more details.
 
 ### Rationale
 
 A custom staging site is available at http://staging-site-[BRANCH] upon pushing your branch (see ops > templates > lxc-manager > staging-create). This site is served by `wrangler` (see ops > templates > owid-site-staging > grapher-refresh.sh). `wrangler` is helpful for testing the functions locally (and possibly for some debugging scenarios on staging servers), but is still not the closest match to the production Cloudflare environment.
 
 When it comes to testing functions in a production-like environment, Cloudflare previews are recommended.
 
-Cloudflare previews are served by Cloudflare (as opposed to `wrangler` on staging sites) and are available at https://[RANDOM_ID].owid-staging.pages.dev. Cloudflare previews do not rely on the `wrangler` CLI and its `.dev.vars` file. Instead, they use the [Cloudflare dashboard to configure environment variables](https://dash.cloudflare.com/078fcdfed9955087315dd86792e71a7e/pages/view/owid/settings/environment-variables), in the same way and place as the production site.
+Cloudflare previews are served by Cloudflare (as opposed to `wrangler` on staging sites) and are available at https://[RANDOM_ID].[PROJECT].pages.dev. Cloudflare previews do not rely on the `wrangler` CLI and its `.dev.vars` file, but they do take the `wrangler.toml` file into account for environment variables. For secrets, they use the [values set via the Cloudflare dashboard](https://dash.cloudflare.com/078fcdfed9955087315dd86792e71a7e/pages/view/owid/settings/environment-variables), in the same way and place as the production site.
 
 This proximity of configurations in the Cloudflare dashboard makes spotting differences between production and preview environments easier - and is one of the reason of using Cloudflare previews in the same project (owid) over using a new project specific to staging.