feat(.github): Create generate-openapi-code-from-typespec (#746)

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> [!IMPORTANT]
> Add GitHub Actions workflow to generate OpenAPI code from TypeSpec,
with environment setup and caching.
> 
>   - **Workflow**:
> - New GitHub Actions workflow `generate-openapi-code-from-typespec`
added.
>     - Triggers on `pull_request` and `push` events.
>   - **Environment Setup**:
>     - Uses `actions/setup-python@v5` to set Python 3.12.
>     - Uses `actions/setup-node@v4` to set up Node.js with npm caching.
> - Configures Poetry with `snok/install-poetry@v1` and sets virtualenvs
in-project.
>   - **Caching**:
> - Caches Poetry virtualenv in `agents-api/.venv` using
`actions/cache@v4`.
>   - **Code Generation**:
> - Runs `scripts/generate_openapi_code.sh` to generate OpenAPI code.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=julep-ai%2Fjulep&utm_source=github&utm_medium=referral)<sup>
for 25acd5b. It will automatically
update as commits are pushed.</sup>

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---------

Co-authored-by: ellipsis-dev[bot] <65095814+ellipsis-dev[bot]@users.noreply.github.com>

.github/workflows/generate-openapi-code-from-typespec

@@ -0,0 +1,56 @@
+name: Generate OpenAPI code
+run-name: ${{ github.actor }} is generating openapi code
+
+on:
+  pull_request:
+    paths:
+      - 'typespec/**'
+  push: 
+    paths:
+      - 'typespec/**'
+
+jobs:
+  Typecheck:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 'latest'
+          cache: npm
+          cache-dependency-path: 'typespec/package-lock.json'
+
+      - name: Install and configure Poetry
+        uses: snok/install-poetry@v1
+
+      - name: Configure Poetry to use .venv
+        run: |
+          cd agents-api
+          poetry config virtualenvs.in-project true
+
+      - name: Cache Poetry virtualenv
+        uses: actions/cache@v4
+        with:
+          path: agents-api/.venv
+          key: ${{ runner.os }}-agents-api-poetry-${{ hashFiles('agents-api/poetry.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-agents-api-poetry-
+
+      - name: Install dependencies
+        run: |
+          cd agents-api
+          poetry install
+
+      - name: Generate openapi code
+        run: |
+          bash scripts/generate_openapi_code.sh
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}