[feature] Allow users to set default interaction policies per status visibility (#3108)

* [feature] Allow users to set default interaction policies

* use vars for default policies

* avoid some code repetition

* unfuck form binding

* avoid bonkers loop

* beep boop

* put policyValsToAPIPolicyVals in separate function

* don't bother with slices.Grow

* oops

mkdocs.yml

@@ -61,8 +61,8 @@ nav:
   - "Home": "index.md"
   - "FAQ": "faq.md"
   - "User Guide":
-      - "user_guide/posts.md"
       - "user_guide/settings.md"
+      - "user_guide/posts.md"
       - "user_guide/search.md"
       - "user_guide/custom_css.md"
       - "user_guide/password_management.md"