POST fleet/asset-sharing/agreements: Asset Sharing Agreements - Flexible roles

The POST fleet/asset-sharing/agreements endpoint has some new features! Adds optional providerOrganizationId, providerOrganizationName, and payer inputs for flexible agreements. The caller determines the creator; the other party must accept or reject. recipientOrganizationName is required only for provider callers. Existing requests retain their defaults. Recipient-payer requests require the flexible operating model. Responses always include payer and createdByParty.