Merge #327: Replace Coveralls with Codecov for coverage reporting

36f98df Replace coveralls with codecov server for coverage report (GideonBature)

Pull request description:

  <!-- You can erase any parts of this template not applicable to your Pull Request. -->

  ### Description

  <!-- Describe the purpose of this PR, what's being adding and/or fixed -->
  This PR migrates our code coverage reporting from Coveralls to Codecov while maintaining all existing functionality.

  ### Notes to the reviewers

  <!-- In this section you can include notes directed to the reviewers, like explaining why some parts
  of the PR were done in a specific way -->

  ### Changelog notice

  <!-- Notice the release manager should include in the release tag message changelog -->
  <!-- See https://keepachangelog.com/en/1.0.0/ for examples -->

  #### Changes
  - **Updated workflow name**: Changed from "Code Coverage" to reflect Codecov integration
  - **Replaced coverage service**: Switched from `coverallsapp/github-action` to `codecov/codecov-action@v4`
  - **Enhanced permissions**: Added necessary permissions for Codecov OIDC authentication:
    - `contents: read`
    - `pull-requests: write`
    - `id-token: write`
  - **Improved configuration**: Added Codecov-specific parameters:
    - `use_oidc: true` for secure tokenless authentication
    - `fail_ci_if_error: false` to prevent CI failures on upload issues
    - `flags: rust` for better organization
    - `name: codecov-bdk-wallet` for clear identification

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `just p` before pushing

  #### New Features:

  * [ ] I've added tests for the new feature
  * [ ] I've added docs for the new feature

  #### Bugfixes:

  * [ ] This pull request breaks the existing API
  * [ ] I've added tests to reproduce the issue which are now passing
  * [x] I'm linking the issue being fixed by this PR

  Closes #320

ACKs for top commit:
  notmandatory:
    ACK 36f98df

Tree-SHA512: 936ad38f329d07dfc6cb70779aac2a13b5e520cb5e80fa26b0fab7d425c0d8a0ed876a4bd55d0fe1654cfb63b03a62aeded3c3b78535b4fb075318fefcbc3211

Author: notmandatory

.github/workflows/code_coverage.yml

@@ -1,15 +1,17 @@
 name: Code Coverage
 
-# Generates code coverage reports using grcov and uploads results to Coveralls.
+# Generates code coverage reports using grcov and uploads results to Codecov.
 # Runs on every push and pull request to track test coverage metrics.
-# Uploads coverage data to Coveralls for tracking and produces an HTML report artifact for download.
+# Uploads coverage data to Codecov for tracking and produces an HTML report artifact for download.
 
 on: [push, pull_request]
 
-permissions: {}
+permissions:
+  contents: read
+  pull-requests: write
 
 jobs:
-  Codecov:
+  Coverage:
     name: Code Coverage
     runs-on: ubuntu-latest
     env:
@@ -40,13 +42,14 @@ jobs:
         run: grcov . --binary-path ./target/debug/ -s . -t lcov --branch --ignore-not-existing --keep-only 'src/**' --ignore 'tests/**' --ignore 'examples/**' -o ./coverage/lcov.info
       - name: Generate HTML coverage report
         run: genhtml -o coverage-report.html --ignore-errors unmapped ./coverage/lcov.info
-      - name: Coveralls upload
-        # Action pinned at tag 2.3.6
-        uses: coverallsapp/github-action@648a8eb78e6d50909eff900e4ec85cab4524a45b
+      - name: Codecov upload
+        uses: codecov/codecov-action@5a1091511ad55cbe89839c7260b706298ca349f7
         with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          file: ./coverage/lcov.info
-          format: lcov
+          files: ./coverage/lcov.info
+          flags: rust
+          name: codecov-bdk-wallet
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail_ci_if_error: false
       - name: Upload artifact
         uses: actions/upload-artifact@v5
         with: