Cleanup version computation, add gisaf.__version__

src/gisaf/__init__.py

@@ -0,0 +1,11 @@
+import importlib.metadata
+
+try:
+    from dunamai import Version, Style
+
+    __version__ = Version.from_git().serialize(style=Style.SemVer, dirty=True)
+except ImportError:
+    # __name__ could be used if the package name is the same
+    # as the directory - not the case here
+    # __version__ = importlib.metadata.version(__name__)
+    __version__ = importlib.metadata.version("gisaf-backend")