[ashish-pandita-sp]

Summary

Adds the ENTITLEMENT_CONNECTION table to the Secure Data Share identity docs.

• identity-er-diagram.md: new ENTITLEMENT_CONNECTION entity with its columns, and relationships to IDENTITY, ACCOUNT, ENTITLEMENT, and SOURCE
• identity-data-dictionary.md: same columns and relationships. One row is an identity, an account, and an entitlement on a source. ID is the connection id. The identity and entitlement line up with IDENTITY_ENTITLEMENTS (IDENTITY_ID = IDENTITY_ENTITLEMENTS.ID, same ENTITLEMENT_ID). The account and entitlement line up with ACCOUNT_ENTITLEMENTS (ACCOUNT_ID = ACCOUNT_ENTITLEMENTS.ID, same ENTITLEMENT_ID).