[fenix] Allow branch enrollment and unenrollment in Nimbus secret menu (https://github.com/mozilla-mobile/fenix/pull/20050)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

app/src/debug/res/raw/initial_experiments.json

@@ -14,24 +14,33 @@
                   }
               },
               {
-                  "slug": "a1",
+                  "slug": "fancy-settings",
                   "ratio": 0,
                   "feature": {
                       "value": {
-                          "settings-title": "settings_title",
+                          "settings-title": "Fancy Settings"
-                          "settings-title-punctuation": "…"
                       },
                       "enabled": true,
                       "featureId": "nimbus-validation"
                   }
               },
               {
-                  "slug": "a2",
+                  "slug": "smiley",
                   "ratio": 0,
                   "feature": {
                       "value": {
-                          "settings-title": "preferences_category_general",
+                          "settings-title-punctuation": "\uD83D\uDE03"
-                          "settings-title-punctuation": "!"
+                      },
+                      "enabled": true,
+                      "featureId": "nimbus-validation"
+                  }
+              },
+              {
+                  "slug": "bundled-text",
+                  "ratio": 0,
+                  "feature": {
+                      "value": {
+                          "settings-title": "preferences_category_general"
                       },
                       "enabled": true,
                       "featureId": "nimbus-validation"
@@ -78,11 +87,11 @@
                   }
               },
               {
-                  "slug": "treatment",
+                  "slug": "edit-menu-icon",
                   "ratio": 0,
                   "feature": {
                       "value": {
-                          "settings-title": "Fancy Settings",
+                          "settings-title": "preferences_category_general",
                           "settings-icon": "ic_edit"
                       },
                       "enabled": true,

app/src/main/java/org/mozilla/fenix/nimbus/NimbusBranchesStore.kt

@@ -50,6 +50,11 @@ sealed class NimbusBranchesAction : Action {
      * @param selectedBranch The selected [Branch] slug for a Nimbus experiment.
      */
     data class UpdateSelectedBranch(val selectedBranch: String) : NimbusBranchesAction()
+
+    /**
+     * Opts out of the branches.
+     */
+    object UpdateUnselectBranch : NimbusBranchesAction()
 }
 
 /**
@@ -75,5 +80,8 @@ private fun nimbusBranchesFragmentStateReducer(
         is NimbusBranchesAction.UpdateSelectedBranch -> {
             state.copy(selectedBranch = action.selectedBranch)
         }
+        is NimbusBranchesAction.UpdateUnselectBranch -> {
+            state.copy(selectedBranch = "")
+        }
     }
 }

app/src/main/java/org/mozilla/fenix/nimbus/controller/NimbusBranchesController.kt

@@ -26,7 +26,14 @@ class NimbusBranchesController(
 ) : NimbusBranchesAdapterDelegate {
 
     override fun onBranchItemClicked(branch: Branch) {
-        experiments.optInWithBranch(experimentId, branch.slug)
+        nimbusBranchesStore.dispatch(
-        nimbusBranchesStore.dispatch(NimbusBranchesAction.UpdateSelectedBranch(branch.slug))
+            if (experiments.getExperimentBranch(experimentId) != branch.slug) {
+                experiments.optInWithBranch(experimentId, branch.slug)
+                NimbusBranchesAction.UpdateSelectedBranch(branch.slug)
+            } else {
+                experiments.optOut(experimentId)
+                NimbusBranchesAction.UpdateUnselectBranch
+            }
+        )
     }
 }