improves create a person with address

* validation: must have an address when 'create a form' is checked;
* minor improvements

src/Bundle/ChillPersonBundle/Entity/Household/HouseholdMember.php

@@ -35,7 +35,7 @@ class HouseholdMember
     /**
      * @ORM\Column(type="date_immutable", nullable=true, options={"default": null})
      * @Serializer\Groups({"read", "docgen:read"})
-     * @Assert\GreaterThan(
+     * @Assert\GreaterThanOrEqual(
      *     propertyPath="startDate",
      *     message="household_membership.The end date must be after start date",
      *     groups={"household_memberships"}
@@ -202,7 +202,7 @@ class HouseholdMember
 
     public function setPosition(?Position $position): self
     {
-        if ($this->position instanceof Position) {
+        if ($this->position instanceof Position && $this->position !== $position) {
             throw new LogicException('The position is already set. You cannot change ' .
                 'a position of a membership');
         }