DEP: Make database dependencies optional

setup.py

@@ -31,10 +31,17 @@
     'test': tests_require,
     'cf': ['compliance-checker>=4.0.0'],
     'netcdf': ['netcdf4'],
+    'db': [
+        'psycopg2',
+        'sqlalchemy>=2.0',  # GeoAlchemy2 requires >=1.4.  SqlAlchemy2 *may* work but has not been tested yet.
+        'GeoAlchemy2',
+        "alembic",
+    ]
 }
 
 extras_require['dev'] = sorted(set(sum([extras_require[k] for k in [
     'test',
+    'db',
     'doc',
     'performance',
     's3',
@@ -100,16 +107,12 @@
         'distributed',
         'jsonschema>=4.18',  # New reference resolution API
         'numpy',
-        'psycopg2',
         'lark',
         'pandas',
         'python-dateutil',
         'pyyaml',
         'rasterio>=1.3.2',  # Warping broken in 1.3.0 and 1.3.1
         'ruamel.yaml',
-        'sqlalchemy>=2.0',  # GeoAlchemy2 requires >=1.4.  SqlAlchemy2 *may* work but has not been tested yet.
-        'GeoAlchemy2',
-        "alembic",
         'toolz',
         'xarray>=0.9',  # >0.9 fixes most problems with `crs` attributes being lost
         'packaging',