Rust Crate v1.2.0

Added

• (schema) Stabilize request cancellation (#1549)
• (unstable-v2) use EnvVariable for terminal auth env (#1522)
• (unstable-v2) Require auth logout support (#1520)
• (unstable-v2) Group v2 auth methods under auth/* (#1519)
• (unstable-v2) require v2 implementation info (#1517)

Fixed

• (unstable-v2) allow null auth capabilities (#1539)
• Deserialization leniency part 2 (#1526)
• (unstable-v2) make mcpServers optional in new sessions (#1523)
• (rust) Clean up Protocol version handling (#1515)

Other

• (unstable-v2) reorder v2 content fields (#1541)
• (unstable-v2) Clean up client schema types (#1540)
• (schema) correct Implementation description (#1518)