feat: add XDC Network and XDC Apothem testnet chain configs

[AnilChinchawale]

Adds XDCMainnet (network xdc) and XDCApothem (xdc-testnet) to chains.go.

XDC is an EVM-compatible L1 (XDPoS) with native Circle USDC supporting EIP-3009. USDC address + EIP-712 domain verified on-chain:

	network	USDC	name / version
mainnet	xdc (50)	0xfA2958CB79b0491CC627c1557F441eF849Ca8eb1	USDC / 2
testnet	xdc-testnet (51)	0xb5AB69F7bBada22B28e79C8FFAECe55eF1c771D4	USDC / 2

gofmt clean, go build ./... passes.

Summary by CodeRabbit

• New Features
  • Added XDC network configurations for USDC on both mainnet and testnet.
  • Included new exported network identifiers and chain settings, including network ID, native USDC address, token decimals, and EIP-3009 domain details.

[coderabbitai]

📝 Walkthrough

Walkthrough

XDC mainnet and testnet chain configurations are added in chains.go and v2/chains.go. The v2 registry also gains a new XDC network identifier and mappings from XDC network IDs to the new configs.

Changes

XDC Chain Support

Layer / File(s)	Summary
XDC network registry entries v2/chains.go	Adds NetworkXDC, defines XDCMainnet and XDCApothem, and maps both XDC network identifiers to their chain configurations in chainConfigByNetwork.
Root XDC chain configs chains.go	Exports XDCMainnet and XDCApothem ChainConfig values in chains.go with XDC network IDs, native Circle USDC addresses, Decimals: 6, and EIP-3009 domain fields.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 Hop hop, XDC lands in the grove,
Mainnet and testnet now both smoothlyোভ?
USDC shines bright with six-decimal cheer,
And bunny hops on through the chain frontier.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change by describing the added XDC mainnet and Apothem chain configs.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@v2/chains.go`:
- Around line 196-202: Add the missing XDC coverage in the chain verification
tests by updating TestGetChainID to include cases for eip155:50 and eip155:51,
and update TestEIP3009Parameters so the evmChains slice includes XDCMainnet and
XDCApothem. Use the existing test helpers in v2/chains_test.go to verify these
new chains resolve correctly and still expose EIP3009Name and EIP3009Version.

🪄 Autofix

❌ Autofix failed (check again to retry)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 0659b01e-b41b-4b38-9a4b-d1b2ffb0c5a4

📥 Commits

Reviewing files that changed from the base of the PR and between cf17264 and d9d3447.

📒 Files selected for processing (2)

• chains.go
• v2/chains.go

🚧 Files skipped from review as they are similar to previous changes (1)

• chains.go

[coderabbitai]

📐 Maintainability & Code Quality | 🟡 Minor

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail

# Inspect test coverage for newly added XDC networks/configs.
fd -a '^chains_test\.go$' v2 | xargs -I{} sh -c '
  echo "== File: {} ==";
  ast-grep outline "{}" --view expanded | sed -n "1,220p";
  rg -n "TestGetChainID|TestEIP3009Parameters|eip155:50|eip155:51|NetworkXDC|NetworkXDCTestnet|XDCMainnet|XDCApothem" "{}";
'

Repository: mark3labs/x402-go

Length of output: 813

---

🏁 Script executed:

sed -n '158,230p' v2/chains_test.go && echo "---SEPARATOR---" && sed -n '334,362p' v2/chains_test.go

Repository: mark3labs/x402-go

Length of output: 2363

---

Add XDC Mainnet and Testnet to chain-config verification tests.

The v2/chains.go changes are internal valid, but the new XDC networks are missing from the coverage in v2/chains_test.go:

• In TestGetChainID, add test cases for eip155:50 (ChainID 50) and eip155:51 (ChainID 51).
• In TestEIP3009Parameters, include XDCMainnet and XDCApothem in the evmChains slice to verify they correctly possess the EIP3009Name and EIP3009Version fields.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@v2/chains.go` around lines 196 - 202, Add the missing XDC coverage in the
chain verification tests by updating TestGetChainID to include cases for
eip155:50 and eip155:51, and update TestEIP3009Parameters so the evmChains slice
includes XDCMainnet and XDCApothem. Use the existing test helpers in
v2/chains_test.go to verify these new chains resolve correctly and still expose
EIP3009Name and EIP3009Version.

[coderabbitai]

An unexpected error occurred while generating fixes: Not Found - https://docs.github.com/rest/git/refs#get-a-reference