linkifier: Support URL templates for linkifiers.

This swaps out url_format_string from all of our APIs and replaces it
with url_template. Note that the documentation changes in the following
commits  will be squashed with this commit.

We change the "url_format" key to "url_template" for the
realm_linkifiers events in event_schema, along with updating
LinkifierDict. "url_template" is the name chosen to normalize
mixed usages of "url_format_string" and "url_format" throughout
the backend.

The markdown processor is updated to stop handling the format string
interpolation and delegate the task template expansion to the uri_template
library instead.

This change affects many test cases. We mostly just replace "%(name)s"
with "{name}", "url_format_string" with "url_template" to make sure that
they still pass. There are some test cases dedicated for testing "%"
escaping, which aren't relevant anymore and are subject to removal.
But for now we keep most of them as-is, and make sure that "%" is always
escaped since we do not use it for variable substitution any more.

Since url_format_string is not populated anymore, a migration is created
to remove this field entirely, and make url_template non-nullable since
we will always populate it. Note that it is possible to have
url_template being null after migration 0422 and before 0424, but
in practice, url_template will not be None after backfilling and the
backend now is always setting url_template.

With the removal of url_format_string, RealmFilter model will now be cleaned
with URL template checks, and the old checks for escapes are removed.

We also modified RealmFilter.clean to skip the validation when the
url_template is invalid. This avoids raising mulitple ValidationError's
when calling full_clean on a linkifier. But we might eventually want to
have a more centric approach to data validation instead of having
the same validation in both the clean method and the validator.

Fixes #23124.

Signed-off-by: Zixuan James Li <p359101898@gmail.com>

web/e2e-tests/realm-linkifier.test.ts

@@ -8,7 +8,7 @@ async function test_add_linkifier(page: Page): Promise<void> {
     await page.waitForSelector(".admin-linkifier-form", {visible: true});
     await common.fill_form(page, "form.admin-linkifier-form", {
         pattern: "#(?P<id>[0-9]+)",
-        url_format_string: "https://trac.example.com/ticket/%(id)s",
+        url_template: "https://trac.example.com/ticket/{id}",
     });
     await page.click("form.admin-linkifier-form button.button");
 
@@ -30,7 +30,7 @@ async function test_add_linkifier(page: Page): Promise<void> {
             page,
             ".linkifier_row span.linkifier_url_format_string",
         ),
-        "https://trac.example.com/ticket/%(id)s",
+        "https://trac.example.com/ticket/{id}",
     );
 }
 
@@ -46,7 +46,7 @@ async function test_add_invalid_linkifier_pattern(page: Page): Promise<void> {
     await page.waitForSelector(".admin-linkifier-form", {visible: true});
     await common.fill_form(page, "form.admin-linkifier-form", {
         pattern: "(foo",
-        url_format_string: "https://trac.example.com/ticket/%(id)s",
+        url_template: "https://trac.example.com/ticket/{id}",
     });
     await page.click("form.admin-linkifier-form button.button");
 
@@ -62,7 +62,7 @@ async function test_edit_linkifier(page: Page): Promise<void> {
     await common.wait_for_micromodal_to_open(page);
     await common.fill_form(page, "form.linkifier-edit-form", {
         pattern: "(?P<num>[0-9a-f]{40})",
-        url_format_string: "https://trac.example.com/commit/%(num)s",
+        url_template: "https://trac.example.com/commit/{num}",
     });
     await page.click(".dialog_submit_button");
 
@@ -78,7 +78,7 @@ async function test_edit_linkifier(page: Page): Promise<void> {
             page,
             ".linkifier_row span.linkifier_url_format_string",
         ),
-        "https://trac.example.com/commit/%(num)s",
+        "https://trac.example.com/commit/{num}",
     );
 }
 
@@ -87,7 +87,7 @@ async function test_edit_invalid_linkifier(page: Page): Promise<void> {
     await common.wait_for_micromodal_to_open(page);
     await common.fill_form(page, "form.linkifier-edit-form", {
         pattern: "#(?P<id>d????)",
-        url_format_string: "????",
+        url_template: "{id",
     });
     await page.click(".dialog_submit_button");
 
@@ -108,7 +108,7 @@ async function test_edit_invalid_linkifier(page: Page): Promise<void> {
         page,
         edit_linkifier_format_status_selector,
     );
-    assert.strictEqual(edit_linkifier_format_status, "Failed: Enter a valid URL.");
+    assert.strictEqual(edit_linkifier_format_status, "Failed: Invalid URL template.");
 
     await page.click(".dialog_cancel_button");
     await page.waitForSelector("#dialog_widget_modal", {hidden: true});
@@ -123,7 +123,7 @@ async function test_edit_invalid_linkifier(page: Page): Promise<void> {
             page,
             ".linkifier_row span.linkifier_url_format_string",
         ),
-        "https://trac.example.com/commit/%(num)s",
+        "https://trac.example.com/commit/{num}",
     );
 }