Only invoke a given cached partial once

Note that this is backed by a LRU cache (which we soon shall see more usage of), so if you're a heavy user of cached partials it may be evicted and
refreshed if needed. But in most cases every partial is only invoked once.

This commit also adds a timeout (the global `timeout` config option) to make infinite recursion in partials
easier to reason about.

```
name              old time/op    new time/op    delta
IncludeCached-10    8.92ms ± 0%    8.48ms ± 1%   -4.87%  (p=0.016 n=4+5)

name              old alloc/op   new alloc/op   delta
IncludeCached-10    6.65MB ± 0%    5.17MB ± 0%  -22.32%  (p=0.002 n=6+6)

name              old allocs/op  new allocs/op  delta
IncludeCached-10      117k ± 0%       71k ± 0%  -39.44%  (p=0.002 n=6+6)
```

Closes #4086
Updates #9588

6 files changed, 23 insertions, 15 deletions

diff --git a/resources/image.go b/resources/image.go
index ea8a21156..547b3305f 100644
--- a/resources/image.go
+++ b/resources/image.go
@@ -33,6 +33,7 @@ import (
 	color_extractor "github.com/marekm4/color-extractor"
 
 	"github.com/gohugoio/hugo/common/paths"
+	"github.com/gohugoio/hugo/identity"
 
 	"github.com/disintegration/gift"
 
@@ -278,7 +279,7 @@ func (i *imageResource) Filter(filters ...any) (images.ImageResource, error) {
 		gfilters = append(gfilters, images.ToFilters(f)...)
 	}
 
-	conf.Key = helpers.HashString(gfilters)
+	conf.Key = identity.HashString(gfilters)
 	conf.TargetFormat = i.Format
 
 	return i.doWithImageConfig(conf, func(src image.Image) (image.Image, error) {
@@ -430,7 +431,7 @@ func (i *imageResource) getImageMetaCacheTargetPath() string {
 	}
 	p1, _ := paths.FileAndExt(df.file)
 	h, _ := i.hash()
-	idStr := helpers.HashString(h, i.size(), imageMetaVersionNumber, cfgHash)
+	idStr := identity.HashString(h, i.size(), imageMetaVersionNumber, cfgHash)
 	p := path.Join(df.dir, fmt.Sprintf("%s_%s.json", p1, idStr))
 	return p
 }
diff --git a/resources/images/config.go b/resources/images/config.go
index 6f562ff8e..09a7016c1 100644
--- a/resources/images/config.go
+++ b/resources/images/config.go
@@ -19,7 +19,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/identity"
 	"github.com/gohugoio/hugo/media"
 
 	"errors"
@@ -139,7 +139,7 @@ func DecodeConfig(m map[string]any) (ImagingConfig, error) {
 
 	i := ImagingConfig{
 		Cfg:     defaultImaging,
-		CfgHash: helpers.HashString(m),
+		CfgHash: identity.HashString(m),
 	}
 
 	if err := mapstructure.WeakDecode(m, &i.Cfg); err != nil {
diff --git a/resources/images/filters_test.go b/resources/images/filters_test.go
index 84c8b540d..a8c5601d6 100644
--- a/resources/images/filters_test.go
+++ b/resources/images/filters_test.go
@@ -16,9 +16,8 @@ package images
 import (
 	"testing"
 
-	"github.com/gohugoio/hugo/helpers"
-
 	qt "github.com/frankban/quicktest"
+	"github.com/gohugoio/hugo/identity"
 )
 
 func TestFilterHash(t *testing.T) {
@@ -26,8 +25,8 @@ func TestFilterHash(t *testing.T) {
 
 	f := &Filters{}
 
-	c.Assert(helpers.HashString(f.Grayscale()), qt.Equals, helpers.HashString(f.Grayscale()))
-	c.Assert(helpers.HashString(f.Grayscale()), qt.Not(qt.Equals), helpers.HashString(f.Invert()))
-	c.Assert(helpers.HashString(f.Gamma(32)), qt.Not(qt.Equals), helpers.HashString(f.Gamma(33)))
-	c.Assert(helpers.HashString(f.Gamma(32)), qt.Equals, helpers.HashString(f.Gamma(32)))
+	c.Assert(identity.HashString(f.Grayscale()), qt.Equals, identity.HashString(f.Grayscale()))
+	c.Assert(identity.HashString(f.Grayscale()), qt.Not(qt.Equals), identity.HashString(f.Invert()))
+	c.Assert(identity.HashString(f.Gamma(32)), qt.Not(qt.Equals), identity.HashString(f.Gamma(33)))
+	c.Assert(identity.HashString(f.Gamma(32)), qt.Equals, identity.HashString(f.Gamma(32)))
 }
diff --git a/resources/internal/key.go b/resources/internal/key.go
index 1b45d4cc4..2b95871aa 100644
--- a/resources/internal/key.go
+++ b/resources/internal/key.go
@@ -13,7 +13,7 @@
 
 package internal
 
-import "github.com/gohugoio/hugo/helpers"
+import "github.com/gohugoio/hugo/identity"
 
 // ResourceTransformationKey are provided by the different transformation implementations.
 // It identifies the transformation (name) and its configuration (elements).
@@ -38,5 +38,5 @@ func (k ResourceTransformationKey) Value() string {
 		return k.Name
 	}
 
-	return k.Name + "_" + helpers.HashString(k.elements...)
+	return k.Name + "_" + identity.HashString(k.elements...)
 }
diff --git a/resources/page/site.go b/resources/page/site.go
index 8daff95ae..90fbd5551 100644
--- a/resources/page/site.go
+++ b/resources/page/site.go
@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"github.com/gohugoio/hugo/common/maps"
+	"github.com/gohugoio/hugo/identity"
 
 	"github.com/gohugoio/hugo/config"
 
@@ -75,6 +76,9 @@ type Site interface {
 
 	// Returns a map of all the data inside /data.
 	Data() map[string]any
+
+	// Returns the identity of this site.
+	GetIdentity() identity.Identity
 }
 
 // Sites represents an ordered list of sites (languages).
@@ -117,6 +121,10 @@ func (t testSite) Current() Site {
 	return t
 }
 
+func (t testSite) GetIdentity() identity.Identity {
+	return identity.KeyValueIdentity{Key: "site", Value: t.l.Lang}
+}
+
 func (t testSite) IsServer() bool {
 	return false
 }
diff --git a/resources/resource_factories/create/remote.go b/resources/resource_factories/create/remote.go
index 1ae5e095b..8f1707ed0 100644
--- a/resources/resource_factories/create/remote.go
+++ b/resources/resource_factories/create/remote.go
@@ -30,7 +30,7 @@ import (
 	"github.com/gohugoio/hugo/common/hugio"
 	"github.com/gohugoio/hugo/common/maps"
 	"github.com/gohugoio/hugo/common/types"
-	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/identity"
 	"github.com/gohugoio/hugo/media"
 	"github.com/gohugoio/hugo/resources"
 	"github.com/gohugoio/hugo/resources/resource"
@@ -235,9 +235,9 @@ func (c *Client) validateFromRemoteArgs(uri string, options fromRemoteOptions) e
 
 func calculateResourceID(uri string, optionsm map[string]any) string {
 	if key, found := maps.LookupEqualFold(optionsm, "key"); found {
-		return helpers.HashString(key)
+		return identity.HashString(key)
 	}
-	return helpers.HashString(uri, optionsm)
+	return identity.HashString(uri, optionsm)
 }
 
 func addDefaultHeaders(req *http.Request) {