Migrate to pyproject.toml; remove __version__

.flake8

@@ -0,0 +1,4 @@
+[flake8]
+max-line-length = 90
+max-complexity = 18
+extend-ignore = E203, E266, E501, E731, B903

pyproject.toml

@@ -1,3 +1,55 @@
+[project]
+name = "flask-marshmallow"
+version = "1.0.0"
+description = "Flask + marshmallow for beautiful APIs"
+readme = "README.rst"
+license = { file = "LICENSE" }
+maintainers = [{ name = "Steven Loria", email = "[email protected]" }]
+classifiers = [
+  "Environment :: Web Environment",
+  "Intended Audience :: Developers",
+  "License :: OSI Approved :: MIT License",
+  "Natural Language :: English",
+  "Programming Language :: Python :: 3",
+  "Programming Language :: Python :: 3.8",
+  "Programming Language :: Python :: 3.9",
+  "Programming Language :: Python :: 3.10",
+  "Programming Language :: Python :: 3.11",
+  "Programming Language :: Python :: 3.12",
+  "Topic :: Internet :: WWW/HTTP :: Dynamic Content",
+]
+requires-python = ">=3.8"
+dependencies = ["Flask", "marshmallow>=3.0.0", "packaging>=17.0"]
+
+[project.urls]
+Issues = "https://github.com/marshmallow-code/flask-marshmallow/issues"
+Funding = "https://opencollective.com/marshmallow"
+
+[project.optional-dependencies]
+docs = [
+  "marshmallow-sqlalchemy>=0.19.0",
+  "Sphinx==7.2.6",
+  "sphinx-issues==3.0.1",
+]
+tests = ["flask-marshmallow[sqlalchemy]", "pytest"]
+dev = ["flask-marshmallow[tests]", "tox", "pre-commit~=3.5"]
+sqlalchemy = ["flask-sqlalchemy>=3.0.0", "marshmallow-sqlalchemy>=0.29.0"]
+
+[build-system]
+requires = ["flit_core<4"]
+build-backend = "flit_core.buildapi"
+
+[tool.flit.sdist]
+include = ["docs/", "tests/", "CHANGELOG.rst", "CONTRIBUTING.rst", "tox.ini"]
+exclude = ["docs/_build/"]
+
 [tool.black]
 line-length = 88
 target-version = ['py38', 'py39', 'py310', 'py311', 'py312']
+
+[tool.pytest.ini_options]
+filterwarnings = [
+  "error",
+  "ignore:The Query\\.get\\(\\) method is considered legacy:sqlalchemy.exc.LegacyAPIWarning",
+  "ignore:distutils Version classes are deprecated\\. Use packaging.version instead\\.:DeprecationWarning:marshmallow",
+]