XDCR versions < 7.0 does not replicate with target cluster version >= 7.1

When the source cluster version is < 7.0 and target cluster version >= 7.1, users are unable to create replication. 

While creating the replication, they get an error on UI:

Error retrieving password on bucket test. err=Error looking up password of bucket test

In v6.6.5 the error is different: 

2022-06-02T12:07:48.645Z ERRO GOXDCR.AdminPort: Error creating replication. errorsMap=map[type:Replication to an Elasticsearch target cluster using XDCR Version 2 (XMEM protocol) is not supported. Use XDCR Version 1 (CAPI protocol) instead.]

Also, the UI does nothing when you click “SAVE” and the dialog stays as it is with no error shown.

There used to be a key "authType" in response to get bucker info which was removed in 7.0. Absence of this key causes XDCR to detect remote cluster as ES cluster. This further causes the code to execute which expects "saslPassword" key. The support for sasl creds at bucket level was removed in 7.0.