Set the project license in config.env; AGPL-3.0 default only for a public GitHub project

- PROJECT_LICENSE (a Gitea license key, or none) is read, checked and never asked
- Without it AGPL-3.0 applies only when GitHub is chosen and the project is public
- The license is applied on Gitea with or without GitHub, and checked against the server first
- Plan and summary name the license and where it came from
- MIL-006 accepted; README and config.env.example document the key
- Tests: new test-license.sh; existing tests use a public project where they expect AGPL-3.0

Task: MIL-006#1
Task: MIL-006#2
Task: MIL-006#3
Task: MIL-006#4
Refs #44
Refs #45
Refs #46
Refs #50

src/lib/plan.sh

@@ -22,8 +22,8 @@ print_plan() {
   say "Plan:"
   if ((STATE[reuse_gitea])); then
     gitea_action="reuse the existing repository (you will be asked to confirm)"
-  elif ((PROJECT[has_github])); then
-    gitea_action="create (${PROJECT[visibility]}) with the $AGPL_LICENSE_KEY license"
+  elif [[ -n ${PROJECT[license]} ]]; then
+    gitea_action="create (${PROJECT[visibility]}) with the ${PROJECT[license]} license$(license_note)"
   else
     gitea_action="create (${PROJECT[visibility]}), empty"
   fi