add script to prune designer files from migrations, add README with acknowledgements

Foxnouns.Backend/Database/prune-designer-cs-files.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+set -e
+
+# Original script by zotan for Iceshrimp.NET
+# Source: https://iceshrimp.dev/iceshrimp/Iceshrimp.NET/src/commit/7c93dcf79dda54fc1a4ea9772e3f80874e6bcefb/Iceshrimp.Backend/Core/Database/prune-designer-cs-files.sh
+
+if [[ $(uname) == "Darwin" ]]; then
+	SED="gsed"
+else
+	SED="sed"
+fi
+
+import="using Microsoft.EntityFrameworkCore.Infrastructure;"
+dbc="    [DbContext(typeof(DatabaseContext))]"
+
+for file in $(find "$(dirname $0)/Migrations" -name '*.Designer.cs'); do
+	echo "$file"
+	csfile="${file%.Designer.cs}.cs"
+	if [[ ! -f $csfile ]]; then
+		echo "$csfile doesn't exist, exiting"
+		exit 1
+	fi
+	lineno=$($SED -n '/^{/=' "$csfile")
+	((lineno+=2))
+	migr=$(grep "\[Migration" "$file")
+	$SED -i "${lineno}i \\$migr" "$csfile"
+	$SED -i "${lineno}i \\$dbc" "$csfile"
+	$SED -i "2i $import" "$csfile"
+	rm "$file"
+done