issue_templates: Redirect feature requests

The existing Feature issue template is tailored for contributors who
understand the process, have insight on benefits and drawbacks.

In practice, that's a minority of the people how use the template. 
For everybody else, the template appears to encourage submission of
features requests without previous community discussion. This often
results in poor quality issue descriptions which lack actual use 
cases and naïvely assert there are no drawbacks. Poor quality issues 
end up being closed, which sends negative vibes, feeding frustration
and unproductive behaviors.

Aiming to avoid the negativity trap and promote community engagement,
point people in the direction of Discourse and the place to discuss
ideas.

Also, add a new Shortcomings template to get more useful information
on the underlying problems motivating the feature request.

.gitlab/issue_templates/Feature.md

@@ -1,22 +1,9 @@
-### Use cases
-<!-- Describe what problem(s) the user is experiencing and that this request
-is trying to solve. -->
+# Ideas for new features are welcome!
 
+Please share your feature ideas in our Discourse in order to discuss them with our community:
 
-### Desired behavior
-<!-- Describe the desired functionality. -->
+https://discourse.gnome.org/tag/nautilus
 
+Quite some evaluation plus refinement has to happen between an idea and creating an actual and detailed plan for a potential implementation. We found that they develop into actionable issues best when they are discussed beforehand.
 
-### Benefits of the solution
-<!-- List the possible benefits of the solution and how it fits in the project. -->
-
-
-### Possible drawbacks
-<!--
-     Describe possible drawbacks of the feature and list how it could affect
-     the project i.e. UI discoverability, complexity, impact in more or less
-     number of users, etc.
--->
-
-<!-- Ignore the text under this line. -->
-/label ~"1. Feature"
+However, if you've got this idea because of an existing problem in the application, please don't forget to report the bug or shortcoming using the respective template.

.gitlab/issue_templates/Shortcoming.md

@@ -0,0 +1,31 @@
+<!--
+    Please test if the shortcoming is overcome in the Nightly version already
+
+    You can install the Nightly version in parallel with the regular version with these instructions:
+
+    1. Make sure that Flatpak is installed (see https://flatpak.org/setup )
+    2. Copy and run the following command in a Terminal:
+
+    flatpak install --from https://nightly.gnome.org/repo/appstream/org.gnome.NautilusDevel.flatpakref
+
+    3) The Nightly version can now be launched from Activities, or with this command: flatpak run org.gnome.NautilusDevel
+-->
+
+# Affected version
+- Nightly flatpak: Yes / No / Can't test it because <!-- Delete the unwanted anwsers -->
+- Other: <!-- Write the distribution you’re using and the version of the app. -->
+
+### Use cases
+<!-- Describe concrete situations in which this application isn't helpful enough.
+     Focus is on the end goal, not the means to get there. 
+     Don't forget to mention any applicable requirements or constrants.
+     Examples from your daily usage are the most useful. -->
+
+### Available features and workarounds
+<!-- How do you manage to achieve your goals with the current version of the application? -->
+
+### Difficulties and insufficiencies
+<!-- Why is the current experience unsatisfying? -->
+
+### Suggested enhancements
+<!-- Optionally . -->