anchor.diff:  stale shard copy.
   
   [float]
  -=== Make index creation resilient to index closing and full cluster crashes (STATUS: UNRELEASED, v5.0.0)
  +=== Make index creation resilient to index closing and full cluster crashes (STATUS: DONE, v5.0.0)
   
   Recovering an index requires a quorum (with an exception for 2) of shard copies to be available to allocate a primary. This means that
   a primary cannot be assigned if the cluster dies before enough shards have been allocated ({GIT}9126[#9126]). The same happens if an index
  
positive.code: To prevent this situation, the primary needs to wait for the master to acknowledge replica shard failures before acknowledging the write to the client. {GIT}14252[#14252]
  
  [float]
  === Safe primary relocations (STATUS: UNRELEASED, v5.0.0)
  
  When primary relocation completes, a cluster state is propagated that deactivates the old primary and marks the new primary as active. As
  cluster state changes are not applied synchronously on all nodes, there can be a time interval where the relocation target has processed the
  
negative.code: chasing the primary being quickly sent back and forth between the nodes, potentially making them both go OOM. {GIT}12573[#12573]
  
  [float]
  === Do not allow stale shards to automatically be promoted to primary (STATUS: DONE, v5.0.0)
  
  In some scenarios, after the loss of all valid copies, a stale replica shard can be automatically assigned as a primary, preferring old data
  to no data at all ({GIT}14671[#14671]). This can lead to a loss of acknowledged writes if the valid copies are not lost but are rather
  