referrals: add "use expiry" option

adds an option when enabling referrals to use the duration of the source
invited (i.e., months, days, hours) for the referral invite. If enabled,
the user won't be able to make a new referral link after it expires. For
referrals enabled for new users via a profile, the clock starts ticking
as soon as the account is created.

api-userpage.go

@@ -746,21 +746,37 @@ func (app *appContext) GetMyReferral(gc *gin.Context) {
 		//    Since this key is shared between users in a profile, we make a copy.
 		user, ok := app.storage.GetEmailsKey(gc.GetString("jfId"))
 		err = app.storage.db.Get(user.ReferralTemplateKey, &inv)
-		if !ok || err != nil {
+		if !ok || err != nil || user.ReferralTemplateKey == "" {
 			app.debug.Printf("Ignoring referral request, couldn't find template.")
 			respondBool(400, false, gc)
 			return
 		}
 		inv.Code = GenerateInviteCode()
+		expiryDelta := inv.ValidTill.Sub(inv.Created)
 		inv.Created = time.Now()
-		inv.ValidTill = inv.Created.Add(REFERRAL_EXPIRY_DAYS * 24 * time.Hour)
+		if inv.UseReferralExpiry {
+			inv.ValidTill = inv.Created.Add(expiryDelta)
+		} else {
+			inv.ValidTill = inv.Created.Add(REFERRAL_EXPIRY_DAYS * 24 * time.Hour)
+		}
 		inv.IsReferral = true
 		inv.ReferrerJellyfinID = gc.GetString("jfId")
 		app.storage.SetInvitesKey(inv.Code, inv)
 	} else if time.Now().After(inv.ValidTill) {
 		// 3. We found an invite for us, but it's expired.
 		//    We delete it from storage, and put it back with a fresh code and expiry.
+		//    If UseReferralExpiry is enabled, we delete it and return nothing.
 		app.storage.DeleteInvitesKey(inv.Code)
+		if inv.UseReferralExpiry {
+			user, ok := app.storage.GetEmailsKey(gc.GetString("jfId"))
+			if ok {
+				user.ReferralTemplateKey = ""
+				app.storage.SetEmailsKey(gc.GetString("jfId"), user)
+			}
+			app.debug.Printf("Ignoring referral request, expired.")
+			respondBool(400, false, gc)
+			return
+		}
 		inv.Code = GenerateInviteCode()
 		inv.Created = time.Now()
 		inv.ValidTill = inv.Created.Add(REFERRAL_EXPIRY_DAYS * 24 * time.Hour)
@@ -771,5 +787,6 @@ func (app *appContext) GetMyReferral(gc *gin.Context) {
 		RemainingUses: inv.RemainingUses,
 		NoLimit:       inv.NoLimit,
 		Expiry:        inv.ValidTill.Unix(),
+		UseExpiry:     inv.UseReferralExpiry,
 	})
 }