Drop support for python 3.9 so we can use match/case

Author: rlskoeser

.github/workflows/unit_tests.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python: ["3.10", "3.11", "3.12", "3.13"]
     defaults:
       run:
         working-directory: .

pyproject.toml

@@ -7,7 +7,7 @@ name = "undate"
 description = "library for working with uncertain, fuzzy, or partially unknown dates and date intervals"
 readme = "README.md"
 license = { text = "Apache-2" }
-requires-python = ">= 3.9"
+requires-python = ">= 3.10"
 dynamic = ["version"]
 dependencies = ["lark[interegular]", "numpy", "convertdate", "strenum; python_version < '3.11'"]
 authors = [
@@ -31,7 +31,6 @@ keywords = [
 classifiers = [
     "Development Status :: 2 - Pre-Alpha",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",