sagemathgh-36561: `pkgs/sage-conf`: Move metadata from `setup.cfg` to `pyproject.toml`
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
- In part split out from sagemath#36489
- Part of sagemath#33577
<!-- If your change requires a documentation PR, please link it
appropriately. -->

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [ ] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation accordingly.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on
- sagemath#12345: short description why this is a dependency
- sagemath#34567: ...
-->
- Depends on sagemath#36533 (which changes setup.cfg, merged here)
- Depends on sagemath#36885

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36561
Reported by: Matthias Köppe
Reviewer(s): François Bissey

Author: Release Manager

.gitignore

@@ -193,6 +193,7 @@ build/bin/sage-build-env-config
 /pkgs/*/*.egg-info
 /pkgs/*/.tox
 
+/pkgs/sage-conf/pyproject.toml
 /pkgs/sage-conf_pypi/sage_root/config.log
 /pkgs/sage-conf_pypi/sage_root/config.status
 /pkgs/sage-conf_pypi/sage_root/local/

build/pkgs/sage_conf/bootstrap

@@ -0,0 +1 @@
+../sagelib/bootstrap

build/pkgs/sage_conf/dependencies

@@ -1 +1 @@
- $(SAGE_ROOT)/pkgs/sage-conf/_sage_conf/_conf.py $(SAGE_ROOT)/pkgs/sage-conf/setup.cfg $(SAGE_ROOT)/pkgs/sage-conf/bin/sage-env-config | $(PYTHON_TOOLCHAIN) $(PYTHON)
+ $(SAGE_ROOT)/pkgs/sage-conf/_sage_conf/_conf.py $(SAGE_ROOT)/pkgs/sage-conf/pyproject.toml $(SAGE_ROOT)/pkgs/sage-conf/bin/sage-env-config | $(PYTHON_TOOLCHAIN) $(PYTHON)

pkgs/sage-conf/.gitignore

@@ -1,4 +1,6 @@
 /_sage_conf/_conf.py
+/setup.cfg
+/pyproject.toml
 /build
 /dist
 /*.egg-info

pkgs/sage-conf/pyproject.toml

@@ -0,0 +1,44 @@
+include(`sage_spkg_versions_toml.m4')dnl' -*- conf-toml -*-
+[build-system]
+requires = [
+    SPKG_INSTALL_REQUIRES_setuptools
+]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "sage-conf"
+description = "Sage: Open Source Mathematics Software: Configuration module for the SageMath library"
+readme = "README.rst"
+dnl Not including the standard metadata from pyproject_toml_metadata.m4
+dnl because sage-conf is GPL v3+.
+license = {text = "GNU General Public License (GPL) v3 or later"}
+authors = [{name = "The Sage Developers", email = "[email protected]"}]
+classifiers = [
+    "Development Status :: 6 - Mature",
+    "Intended Audience :: Education",
+    "Intended Audience :: Science/Research",
+    "License :: OSI Approved :: GNU General Public License v2 or later (GPLv2+)",
+    "Operating System :: POSIX",
+    "Operating System :: MacOS :: MacOS X",
+    "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: Implementation :: CPython",
+    "Topic :: Scientific/Engineering :: Mathematics",
+]
+urls = {Homepage = "https://www.sagemath.org"}
+requires-python = ">=3.9, <3.12"
+dynamic = ["version"]
+
+[project.scripts]
+sage-config = "sage_conf:_main"
+
+[tool.setuptools]
+packages = ["_sage_conf"]
+py-modules = ["sage_conf"]
+script-files = ["bin/sage-env-config"]
+include-package-data = false
+
+[tool.setuptools.dynamic]
+version = {file = ["VERSION.txt"]}