The v2 arize_phoenix preset read PHOENIX_PROJECT_NAME once at startup into a
static resource attribute, silently dropping the per-key/team project routing
v1 supported. Route it via Phoenix's x-project-name OTLP/HTTP header instead:
the env var stays the global default, and a phoenix_project_name (or
phoenix_project_name_override) in key/team metadata sends that key's traces
to the named project.
The project comes only from user_api_key_auth_metadata (server-set at auth),
never from client request metadata or StandardCallbackDynamicParams, since
choosing the telemetry destination is a data-exfiltration primitive. The
header is appended to the exporter's static headers rather than replacing
them, so the preset's Authorization survives, and it is gated to OTLP/HTTP
exporters because Phoenix only reads it on /v1/traces.
Also unban the bare phoenix_project_name fields from the request-body gate:
the proxy integrations ignore them (only user_api_key_auth_metadata routes,
and that stays banned), so rejecting them just broke SDK-style callers.