software/theia: set THEIA_WEBVIEW_EXTERNAL_ENDPOINT

This disable a theia security feature of using a different hostname for
each webview. By defaut, for each webview, thiea generate an unique
hostname that when using vifib frontends would be something like
https://uuid.webview.softinstXXX.host.vifib.net but that's not usable in
our case because we cannot create frontends for a subdomain (also we
don't have certificates for such domain).

Configure THEIA_WEBVIEW_EXTERNAL_ENDPOINT to something less secure, but
working in our environment. This fixes embedded jupyter notebooks and
other web views.

software/theia/buildout.hash.cfg

@@ -15,7 +15,7 @@
 
 [instance]
 filename = instance.cfg.in
-md5sum = 99dfaa031e58518326b731e9218aa425
+md5sum = 42d21dc3f5d3e57e142eea8e016195f0
 
 [yarn.lock]
 filename = yarn.lock

software/theia/instance.cfg.in

@@ -121,7 +121,7 @@ recipe = slapos.cookbook:userinfo
 recipe = slapos.cookbook:wrapper
 wrapper-path = $${directory:services}/$${:_buildout_section_name_}
 command-line =
-  env LC_ALL=C.UTF-8 TMP=$${directory:tmp} THEIA_SHELL=$${theia-shell:wrapper-path} ${theia-wrapper:rendered} --hostname=$${:hostname} --port=$${:port} $${directory:project}
+  env LC_ALL=C.UTF-8 TMP=$${directory:tmp} THEIA_WEBVIEW_EXTERNAL_ENDPOINT='{{hostname}}' THEIA_SHELL=$${theia-shell:wrapper-path} ${theia-wrapper:rendered} --hostname=$${:hostname} --port=$${:port} $${directory:project}
 
 ip =  $${instance-parameter:ipv4-random}
 hostname =  $${:ip}