specifically, during bulk uploads an object is validated many times before saving
dirty checks only reset on save meaning after setting the UPRN the process_uprn_change code would run on every validation, leading to many calls
to solve this, add a flag to the log which blocks further UPRN calls if it tries to set the uprn twice to the same value. if different values are returned then continue checking
this offers a tradeoff between number of api calls and also should not break existing functionality