🔧 Update package metadata, drop support for Python 3.6, move build internals from Flit to Hatch (#5240)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
+        python-version: ["3.7", "3.8", "3.9", "3.10"]
       fail-fast: false
 
     steps:
@@ -26,14 +26,10 @@ jobs:
         with:
           path: ${{ env.pythonLocation }}
           key: ${{ runner.os }}-python-${{ env.pythonLocation }}-${{ hashFiles('pyproject.toml') }}-test-v02
-      - name: Install Flit
-        if: steps.cache.outputs.cache-hit != 'true'
-        run: pip install flit
       - name: Install Dependencies
         if: steps.cache.outputs.cache-hit != 'true'
-        run: flit install --symlink
+        run: pip install -e .[all,dev,doc,test]
       - name: Lint
-        if: ${{ matrix.python-version != '3.6' }}
         run: bash scripts/lint.sh
       - name: Test
         run: bash scripts/test.sh