Fix HTTP/2 coalescing cross-routing in targetinfo.lua

Hosts that share one wildcard cert (e.g. hassio.718it.biz and
metrics.718it.biz under *.718it.biz) resolve to the same IP, so browsers
coalesce them onto a single HTTP/2 connection. The SSL request_domain
phase resolves the connection's first host and caches it in
ngx.ctx.targetInfo; the unguarded `if targetInfo then return targetInfo`
then handed that first host's target to every coalesced request on the
connection -- e.g. hassio.718it.biz served from metrics' 192.168.1.8:8088.

Confirmed via debug logging: for GET requests to hassio.718it.biz on a
coalesced connection, ngx.ctx already held metrics' IP and the function
short-circuited to it.

Guard the reuse by host: only return the cached target when
ngx.ctx.targetInfo_domain matches the requested domain, and record that
domain whenever a target is resolved. A coalesced request for a different
host now re-resolves against its actual Host header.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ops/nginx_conf/targetinfo.lua

@@ -13,7 +13,14 @@ print("In targetInfo module")
 
 -- Main function of the module
 function M.get(ngx, domain, targetInfo)
-    if targetInfo then
+    -- Reuse a previously-resolved target ONLY when it was resolved for this
+    -- exact host. HTTP/2 connection coalescing lets a browser serve several
+    -- hostnames that share one wildcard cert (e.g. *.718it.biz) over a single
+    -- connection; the SSL phase (request_domain) resolves and caches the
+    -- connection's first host in ngx.ctx.targetInfo. Without the domain check
+    -- below, every coalesced request on that connection would be handed the
+    -- first host's target -- e.g. hassio.718it.biz served from metrics.718it.biz.
+    if targetInfo and ngx.ctx.targetInfo_domain == domain then
         return targetInfo
     end
 
@@ -68,6 +75,10 @@ function M.get(ngx, domain, targetInfo)
     end
 
     ngx.ctx.targetInfo = res
+    -- Remember which host this target was resolved for, so the reuse guard at
+    -- the top can tell a genuine cache hit from a coalesced request for a
+    -- different host on the same connection.
+    ngx.ctx.targetInfo_domain = domain
     ngx.ctx.toAllow = true
 
     return res