[proxy] forward Bedrock cost-allocation metadata + per-provider metadata_disabled

Stamp the caller's user and authorizing group onto AWS Bedrock requests via the
X-Amzn-Bedrock-Request-Metadata header (reusing the JSONMetadata identity-inject
shape with a Bedrock-charset sanitizer), so spend can be attributed in AWS Cost
Management. Add a per-provider metadata_disabled flag (default off) that
suppresses identity metadata injection while leaving catalog routing headers
intact.

shared/management/http/api/openapi.yml

@@ -5164,6 +5164,10 @@ components:
           type: boolean
           description: Whether upstream TLS certificate verification is skipped when the proxy dials this provider's URL. Intended for self-hosted / internal gateways behind a private or self-signed certificate.
           example: false
+        metadata_disabled:
+          type: boolean
+          description: Whether identity metadata injection is disabled for this provider. When enabled (the default), the proxy stamps the caller's user and authorizing group onto upstream requests as provider-specific metadata (e.g. AWS Bedrock's X-Amzn-Bedrock-Request-Metadata header). Set true to suppress it.
+          example: false
         created_at:
           type: string
           format: date-time
@@ -5184,6 +5188,7 @@ components:
         - models
         - enabled
         - skip_tls_verification
+        - metadata_disabled
         - created_at
         - updated_at
     AgentNetworkProviderRequest:
@@ -5240,6 +5245,10 @@ components:
           type: boolean
           description: Skip upstream TLS certificate verification when the proxy dials this provider's URL. For self-hosted / internal gateways behind a private or self-signed certificate. Defaults to false. When omitted on update, the stored value is left unchanged.
           example: false
+        metadata_disabled:
+          type: boolean
+          description: Disable identity metadata injection (the caller's user + authorizing group) for this provider. Defaults to false (metadata is injected). When omitted on update, the stored value is left unchanged.
+          example: false
       required:
         - provider_id
         - name

shared/management/http/api/types.gen.go

@@ -2227,6 +2227,9 @@ type AgentNetworkProvider struct {
 	// IdentityHeaderUserId Wire header name the proxy stamps with the caller's display identity (user email or peer name) when the catalog entry's HeaderPair is `customizable`. Empty disables stamping for this dimension. Ignored when the catalog entry has a fixed HeaderPair (e.g. LiteLLM, Portkey). Used today by Bifrost: typical values are `x-bf-lh-netbird_user_id` (always-on log metadata) or `x-bf-dim-netbird_user_id` (Prometheus / OTEL — requires the label to be pre-declared in the gateway's `client.prometheus_labels` config).
 	IdentityHeaderUserId *string `json:"identity_header_user_id,omitempty"`
 
+	// MetadataDisabled Whether identity metadata injection is disabled for this provider. When enabled (the default), the proxy stamps the caller's user and authorizing group onto upstream requests as provider-specific metadata (e.g. AWS Bedrock's X-Amzn-Bedrock-Request-Metadata header). Set true to suppress it.
+	MetadataDisabled bool `json:"metadata_disabled"`
+
 	// Models Models exposed through this endpoint, with the operator's per-1k input/output prices. Empty means all catalog models are allowed at catalog prices.
 	Models []AgentNetworkProviderModel `json:"models"`
 
@@ -2278,6 +2281,9 @@ type AgentNetworkProviderRequest struct {
 	// IdentityHeaderUserId Wire header name for the caller's display identity. See AgentNetworkProvider.identity_header_user_id. When omitted on a request, the stored value is left unchanged; pass an empty string explicitly to clear it (which disables stamping for this dimension).
 	IdentityHeaderUserId *string `json:"identity_header_user_id,omitempty"`
 
+	// MetadataDisabled Disable identity metadata injection (the caller's user + authorizing group) for this provider. Defaults to false (metadata is injected). When omitted on update, the stored value is left unchanged.
+	MetadataDisabled *bool `json:"metadata_disabled,omitempty"`
+
 	// Models Models exposed through this endpoint, with the operator's per-1k input/output prices. Empty means all catalog models are allowed at catalog prices.
 	Models *[]AgentNetworkProviderModel `json:"models,omitempty"`