Resolve a hashed email (HEM) or plain email address to stored identity data.
Provide either hem or email (not both).

Hash type. A hem is matched by algorithm: SHA-256 (64 hex characters)
or MD5 (32 hex characters). The algorithm is inferred from the digest length;
pass hem_type to set it explicitly (it is then validated against the hem).
When email is provided instead, it is normalized and hashed for you.

Filtering and projection. Optional filter and select params apply the
same grammar as /api/v1/events, evaluated against the single resolved record:

• select projects a subset of fields (comma-separated). Absent fields are omitted.
• filter (<field>:<op>:<value>, , = AND, | = OR within a group; ops
  eq, ne, like, not_null) decides whether the record is returned. If the
  record does not match, the endpoint responds 404 (no record). Example —
  business-email records only:
  filter=current_business_email:ne:""|business_emails:ne:""|is_email_business:eq:"true".
  Quote literal values (is_email_business:eq:"true").

Billing. Metered on egress as contact_record (the same meter as a
contact query or audience download, not the events resolution_* tiers):
a 200 that returns a record bills one contact record; a 404 (not found
or filtered out) bills nothing. select projects fields but does not change
the meter.