[FEATURE] Per-Stream and Connection Flow Control for HTTP2

[gimlet2]

Feature Description

Implement flow control mechanisms for both streams and connection as per HTTP2 specification.

Problem/Use Case

Flow control is required to prevent resource exhaustion and to balance throughput and fairness across streams.

Proposed Solution

• Support WINDOW_UPDATE frames
• Enforce initial window sizes and dynamic updates
• Handle flow control errors

Code Example

server.sendWindowUpdate(streamId = 1, increment = 1024)

Alternatives Considered

• No flow control (not compliant)

Additional Context

• Would this be a breaking change? No
• Priority: High
• Related to HTTP2 support #3 HTTP2 support

Related Issues/PRs

• HTTP2 support #3 HTTP2 support