Translates a SCIM 2.0 PATCH request body (RFC 7644 §3.5.2) into a structured input describing both attribute updates and relationship-level operations:

%{
  attrs: %{first_name: "Alicia"},
  relationships: [
    {:append, :memberships, [%{user_id: "u1"}]},
    {:remove_where, :memberships, %{user_id: %{eq: "u2"}}}
  ]
}

The router applies attrs via the resource's update action and each relationship op as either a manage_relationship/4 call or a custom load+destroy/update step.

Supported operations

• add / replace with no path — value is treated as a partial SCIM resource and decoded via AshScim.Decoder. Only attribute changes are applied (relationship arrays in path-less ops are ignored, since the semantics of "add a partial resource that includes a member list" aren't well-defined).
• add / replace / remove with a simple path (e.g. active, name.givenName) — maps to the corresponding Ash attribute.
• add path: "emails" value: [...] — append-style relationship op.
• replace path: "emails" value: [...] — full-replace relationship op.
• remove path: "emails[value eq "x"]" — load-and-destroy op against the related resource matching the bracket filter.

When the multivalued declares mirror_primary_to:, the patch result also carries a :mirror_sync post-op (or a synchronously-computed attr write for replace) that keeps the parent's mirrored scalar in sync with the primary entry's value.