chore: migrate to codecov (#344)

# Description

<!-- Please provide a general summary of your PR changes and link any
related issues or other pull requests. -->

# Testing

<!-- 
Please provide details on how you tested this code. See below.

- All pull requests must be tested (unit tests where possible with
accompanying cassettes, or provide a screenshot of end-to-end testing
when unit tests are not possible)
- New features must get a new unit test
- Bug fixes/refactors must re-record existing cassettes 
-->

# Pull Request Type

Please select the option(s) that are relevant to this PR.

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Improvement (fixing a typo, updating readme, renaming a variable
name, etc)

Author: Justintime50

.github/workflows/ci.yml

@@ -24,12 +24,11 @@ jobs:
         run: just install
       - name: run tests
         run: EASYPOST_TEST_API_KEY=123 EASYPOST_PROD_API_KEY=123 just test
-      - name: Coveralls
+      - name: Coverage
         if: github.ref == 'refs/heads/master'
-        uses: coverallsapp/github-action@master
+        uses: codecov/codecov-action@v5
         with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          path-to-lcov: './coverage/lcov/easypost-ruby.lcov'
+          token: ${{ secrets.CODECOV_TOKEN }}
   lint:
     runs-on: ubuntu-latest
     steps:

README.md

@@ -1,7 +1,7 @@
 # EasyPost Ruby Client Library
 
 [![Build Status](https://github.com/EasyPost/easypost-ruby/workflows/CI/badge.svg)](https://github.com/EasyPost/easypost-ruby/actions?query=workflow%3ACI)
-[![Coverage Status](https://coveralls.io/repos/github/EasyPost/easypost-ruby/badge.svg?branch=master)](https://coveralls.io/github/EasyPost/easypost-ruby?branch=master)
+[![codecov](https://codecov.io/gh/EasyPost/easypost-ruby/graph/badge.svg?token=NuKtbPVJMX)](https://codecov.io/gh/EasyPost/easypost-ruby)
 [![Gem Version](https://badge.fury.io/rb/easypost.svg)](https://badge.fury.io/rb/easypost)
 
 EasyPost, the simple shipping solution. You can sign up for an account at <https://easypost.com>.