Make Page an interface

The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue  #5074, "pages from other data sources".

But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.

Most notable changes:

* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
  This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
  This improves the taxonomy template `.Title` situation and make common template constructs much simpler.

See #5074
Fixes #5763
Fixes #5758
Fixes #5090
Fixes #5204
Fixes #4695
Fixes #5607
Fixes #5707
Fixes #5719
Fixes #3113
Fixes #5706
Fixes #5767
Fixes #5723
Fixes #5769
Fixes #5770
Fixes #5771
Fixes #5759
Fixes #5776
Fixes #5777
Fixes #5778

1 files changed, 5 insertions, 5 deletions

diff --git a/hugolib/pagebundler_capture.go b/hugolib/pagebundler_capture.go
index 446d3b0c7..17a4b865a 100644
--- a/hugolib/pagebundler_capture.go
+++ b/hugolib/pagebundler_capture.go
@@ -116,7 +116,7 @@ func newCapturer(
 // these channels.
 type captureResultHandler interface {
 	handleSingles(fis ...*fileInfo)
-	handleCopyFiles(fis ...pathLangFile)
+	handleCopyFile(fi pathLangFile)
 	captureBundlesHandler
 }
 
@@ -141,10 +141,10 @@ func (c *captureResultHandlerChain) handleBundles(b *bundleDirs) {
 	}
 }
 
-func (c *captureResultHandlerChain) handleCopyFiles(files ...pathLangFile) {
+func (c *captureResultHandlerChain) handleCopyFile(file pathLangFile) {
 	for _, h := range c.handlers {
 		if hh, ok := h.(captureResultHandler); ok {
-			hh.handleCopyFiles(files...)
+			hh.handleCopyFile(file)
 		}
 	}
 }
@@ -444,7 +444,7 @@ func (c *capturer) handleNonBundle(
 				}
 				c.handler.handleSingles(f)
 			} else {
-				c.handler.handleCopyFiles(fi)
+				c.handler.handleCopyFile(fi)
 			}
 		}
 	}
@@ -457,7 +457,7 @@ func (c *capturer) copyOrHandleSingle(fi *fileInfo) {
 		c.handler.handleSingles(fi)
 	} else {
 		// These do not currently need any further processing.
-		c.handler.handleCopyFiles(fi)
+		c.handler.handleCopyFile(fi)
 	}
 }