implement invalidityEndsContract flag (default TRUE)

If this flag is set (default), the contract ends when invalidity happens, i.e. the survival probability of the contract is
   px = 1 - qx - ix
If the flag is set to FALSE, a dread-disease/disability/morbidity claim is paid with propbability ix, but the contract continues, potentially paying our further disease claims in the future

R/InsuranceParameters.R

@@ -119,6 +119,7 @@ InsuranceContract.ParameterDefaults = list(
     ActuarialBases = list(
         mortalityTable = NULL,
         invalidityTable = NULL,
+        invalidityEndsContract = FALSE,         # Whether a claim for disease ends the contract or not
         i = 0.00,                               # guaranteed interest rate
         balanceSheetDate = as.Date("1900-12-31"),  # Balance sheet date (for the calculation of the balance sheet reserves, year is irrelevant)
         balanceSheetMethod = "30/360",

R/InsuranceTarif.R

@@ -106,8 +106,13 @@ InsuranceTarif = R6Class(
         i = rep(0, length(q));
       }
       i = pad0(i, length(q));
-      # TODO: Implement case where invalidity/disease does NOT end the contract!
-      df = data.frame(age = ages, q = q, i = i, p = 1 - q - i, row.names = ages - age)
+      # invalidity/disease does NOT end the contract if flag is set!
+      if (params$ActuarialBases$invalidityEndsContract) {
+        p = 1 - q - i
+      } else {
+        p = 1 - q
+      }
+      df = data.frame(age = ages, q = q, i = i, p = p, row.names = ages - age)
       df
     },