Let an entrypoint's description be edited in place (closes #392)

An entrypoint's description was set when it was added and could never change, so renaming one meant deleting it and adding a new one with a new URL every sender had to be given again. Each entrypoint on the webhook page now has an Edit button, in the shared secondary style, that opens its description in place with Save and Cancel and keeps its URL. The save goes through the same login, CSRF and ownership checks as the other entrypoint actions; an empty description shows as "Entrypoint". Activate and deactivate now write only the active column, so they cannot undo an edit. Tests cover each, through the router and the browser.

Model: opus-5-5

README.md

@@ -1328,15 +1328,18 @@ under the real policy and checks that: both add forms stay hidden until Add is
 clicked; choosing Slack in the add target form leaves the HTTP fields out of
 what it submits, also after leaving the page and going back to it, when the
 browser restores the choice; the Copy button beside an entrypoint URL reads
-"Copied" once clicked; an event expands and collapses, and so do a delivery's
+"Copied" once clicked; an entrypoint's Edit button shows its edit form in place
+of its description and hides until the form closes, Cancel hides the form and
+drops what was typed, as does leaving the page and going back to it, and Save
+changes the description; an event expands and collapses, and so do a delivery's
 attempts inside it; and at phone width the menu button opens and closes the
-mobile menu. It also fails if the browser reports a console warning or error,
-an uncaught exception, or anything the policy refused. `make check` and the
-image build lint it but do not run it, and `make test` leaves it out (its file
-is built only with the `browser` build tag). Run it with `make test-browser`
-after changing `templates/` or `static/js/`: that builds `Dockerfile.browser`,
-which runs the test in a digest-pinned headless browser image, so the host
-needs no browser.
+mobile menu. It also fails if the browser reports a console warning or error, an
+uncaught exception, or anything the policy refused. `make check` and the image
+build lint it but do not run it, and `make test` leaves it out (its file is
+built only with the `browser` build tag). Run it with `make test-browser` after
+changing `templates/` or `static/js/`: that builds `Dockerfile.browser`, which
+runs the test in a digest-pinned headless browser image, so the host needs no
+browser.
 
 The package's tarball is committed as `3p/alpinejs-csp-3.14.9.tgz`, byte for
 byte as the npm registry publishes it. It is a dependency, not this repo's build
@@ -2929,6 +2932,7 @@ returns to the page that was asked for.
 | `POST` | `/hook/{id}/deliveries/{deliveryID}/replay` | Replay a finished delivery: creates a new delivery for the same event against the target's current configuration (30 per minute per bucket, then `429`) |
 | `POST` | `/hook/{id}/events/{eventID}/resubmit` | Resubmit a stored event: creates a new event copying it and fans that out to every currently active target (30 per minute per bucket, then `429`) |
 | `POST` | `/hook/{id}/entrypoints` | Add entrypoint to webhook |
+| `POST` | `/hook/{id}/entrypoints/{entrypointID}/edit` | Change an entrypoint's description; its URL stays the same |
 | `POST` | `/hook/{id}/entrypoints/{entrypointID}/delete` | Delete an entrypoint |
 | `POST` | `/hook/{id}/entrypoints/{entrypointID}/toggle` | Enable or disable an entrypoint |
 | `POST` | `/hook/{id}/targets`     | Add target to webhook |