doc: improved DOI handling for URLS

Direct links to papers should preferably be done
using DOI links. Publishers may (at will) change
their URLs but they *will* obey doi.org/<doi>
links meaning that links to published articles
with DOI's will always be stable using:
doi.org/<doi> links.

I uncovered this link by doing make linkcheck
which caused problems for the changed link
(in feature/ulmf).

Signed-off-by: Nick Papior <nickpapior@gmail.com>

Author: zerothi

docs/conf.py

@@ -116,7 +116,11 @@
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 import sphinx_rtd_theme
-extensions = ['recommonmark', "sphinx_rtd_theme"]
+extensions = [
+    'recommonmark',
+    "sphinx_rtd_theme",
+    "sphinx.ext.extlinks",
+]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
@@ -139,6 +143,14 @@
 # so a file named "default.css" will overwrite the builtin "default.css".
 #html_static_path = ['_static']
 
+
+# Short hand external links
+# Allows smoother transitioning for commonly used articles and sites
+extlinks = {
+    'doi': ('https://doi.org/%s', '%s'),
+}
+
+
 # -- Options for MAN output -------------------------------------------------
 
 import os

docs/features/ulfm.rst

@@ -107,7 +107,7 @@ please use:
     J. Dongarra: Post-failure recovery of MPI communication
     capability: Design and rationale. IJHPCA 27(3): 244-254 (2013).*
 
-Available from: https://journals.sagepub.com/doi/10.1177/1094342013488238.
+Available from: :doi:`10.1177/1094342013488238`.
 
 Building ULFM support in Open MPI
 ---------------------------------