feat: increase max RPC connections to 1000

[LesnyRumcajs]

Summary of changes

Changes introduced in this pull request:

• increased the max connections for RPC server to 1000 after discussing with ChainLove
• this can be further modified by an env variable
• this should prevent the server seemingly hanging on new connections

Reference issue to close (if applicable)

Closes #6527

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• New Features

  • Increased maximum RPC server connections to 1000, now configurable via environment variable for flexible deployment configurations.

• Documentation

  • Added environment variable reference documentation with default and example values for RPC connection configuration.

[coderabbitai]

Walkthrough

This PR adds configurable RPC server connection limits via the FOREST_RPC_MAX_CONNECTIONS environment variable, defaulting to 1000. Changes include implementation, documentation, and changelog entries.

Changes

Cohort / File(s)	Summary
Documentation CHANGELOG.md, docs/docs/users/reference/env_variables.md	Added changelog entry and documentation for new FOREST_RPC_MAX_CONNECTIONS environment variable with default value of 1000.
RPC Configuration src/rpc/mod.rs	Implemented DEFAULT_MAX_CONNECTIONS static that reads from FOREST_RPC_MAX_CONNECTIONS environment variable and applies the limit to RPC server configuration.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

RPC

Suggested reviewers

• hanabi1224
• sudo-shashank

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and concisely describes the main change: increasing the maximum RPC connections to 1000, which is the primary focus of the changeset.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch increase-max-default-conns-rpc

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[coderabbitai]

Actionable comments posted: 2

🤖 Fix all issues with AI agents

In `@CHANGELOG.md`:
- Line 56: Update the changelog entry that currently references issue `#6527` so
it references PR `#6528` instead: replace the link text and URL
`[`#6527`](https://github.com/ChainSafe/forest/issues/6527)` with
`[`#6528`](https://github.com/ChainSafe/forest/pull/6528)` in the existing
changelog line that mentions increasing RPC max connections.

In `@src/rpc/mod.rs`:
- Around line 469-476: DEFAULT_MAX_CONNECTIONS currently accepts 0 from
FOREST_RPC_MAX_CONNECTIONS which would disable connections; update the LazyLock
initializer for DEFAULT_MAX_CONNECTIONS so that after parsing the env var you
filter out non‑positive values (e.g., require parsed > 0) and only use the
parsed value when positive, otherwise fall back to the default 1000; refer to
DEFAULT_MAX_CONNECTIONS, the LazyLock::new closure,
env::var("FOREST_RPC_MAX_CONNECTIONS") and the parse handling to locate and
change the logic.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 63.32%. Comparing base (5157235) to head (2c6db24).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/rpc/mod.rs	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/rpc/mod.rs	80.57% <85.71%> (+0.15%)	⬆️

... and 8 files with indirect coverage changes

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