fix(site/htaccess) only use Apache mod_rewrite by replacing RedirectMatch by RewriteRule directives

[dduportal]

Related to jenkins-infra/helpdesk#2649 (comment) and jenkins-infra/helpdesk#4311

After a discussion with @daniel-beck , we realized that some of the issues on the new update center could be solved using smart request distribution on Apache.

The mix of mod_rewrite (RewriteRule) and mod_alias (RedirectMatch ) in the generated htaccess files makes the rules ordering hard to determine as Apache evaluates all rewrite rules and apply the module's own internal priority, and then evaluate the redirect matchings.

We were forced to use RedirectMatch in #790 to ensure the new UC fallback to mirrors.updates.jenkins.io was working as expected without breaking existing redirections.

Using rewrite rules allows more powerful setup such as using internal variables, applying conditions, etc.

This PR:

• Add test case to cover all current RedirectMatch rules (and the test works obviously)
• Replaces the RedirectMatch rules by RewriteRule directives (with test still passing)
• Changing the new UC fallback rule to a RewriteRule which tests the absence of the file specified by the request in order to send to the mirrors. As such, if we copy any file (such as uctest.json or /download/**/*.html) in the Apache document roots, then we can control which files are served from Azure or from the mirrors.

[dduportal]

@daniel-beck shall we test this change on the current production (pkg VM) before reviewing/merging this PR? Or do you think it's enough to go as it?

[daniel-beck]

@dduportal Up to you. I kinda accepted a mess in the wrapper files in this repo already 😉

[dduportal]

@dduportal Up to you. I kinda accepted a mess in the wrapper files in this repo already 😉

Better safe than sorry (on this service): I'll check with @smerle33 and we'll test a manually modified .htaccess before merging this PR then.

Thanks @daniel-beck !

[dduportal]

Tested in production (pkg VM) with the help of @smerle33:

diff -u .htaccess .htaccess.bkp 
--- .htaccess   2024-10-21 15:18:30.760592178 +0000
+++ .htaccess.bkp       2024-10-21 15:13:34.189052454 +0000
@@ -511,9 +511,9 @@
 # download/* directories contain virtual URL spaces for redirecting download traffic to mirrors.
 
 # 'latest' need special handling here since they're not getting mirrored properly to get.jenkins.io
-RewriteRule ^download/war/latest/jenkins[.]war$ https://updates.jenkins.io/latest/jenkins.war [NC,L,R=302]
-RewriteRule ^download/plugins/(.*)/latest/(.+)[.]hpi$ https://updates.jenkins.io/latest/$2.hpi [NC,L,R=302]
+RedirectMatch 302 /download/war/latest/jenkins[.]war$ https://updates.jenkins.io/latest/jenkins.war
+RedirectMatch 302 /download/plugins/(.*)/latest/(.+)[.]hpi$ https://updates.jenkins.io/latest/$2.hpi
 
-RewriteRule ^download/war/([0-9]+[.][0-9]+[.][0-9]+/jenkins)[.]war$ https://get.jenkins.io/war-stable/$1.war [NC,L,R=302]
-RewriteRule ^download/war/(.+)[.]war$ https://get.jenkins.io/war/$1.war [NC,L,R=302]
-RewriteRule ^download/plugins/(.+)[.]hpi$ https://get.jenkins.io/plugins/$1.hpi [NC,L,R=302]
+RedirectMatch 302 /download/war/([0-9]+[.][0-9]+[.][0-9]+/jenkins)[.]war$ https://get.jenkins.io/war-stable/$1.war
+RedirectMatch 302 /download/war/(.+)[.]war$ https://get.jenkins.io/war/$1.war
+RedirectMatch 302 /download/plugins/(.+)[.]hpi$ https://get.jenkins.io/plugins/$1.hpi

We triggered our monitoring + did a few manual curl request: LGT(Us). We're proceeding to merge and deploy