Add module for allowed signers file (#7)

* Add `AllowedSigner` struct

* Add test for `Display` of `AllowedSigner`

* Implement `Display` for `AllowedSigner`

* Add `AllowedSignersFile`

* Add TODO

* Export `AllowedSigner` and `AllowedSignersFile`

* Make fields public

* Make write fn public

* Use constructor for `AllowedSignersFile`

* Add test for writing allowed signers file

* Write trailing newline to allowed signers file

* Move example signers into fixtures

* Add test to ensure existing content is overriden

* Benchmark writing the signers file

* Add benchmark workflow again

Author: SRv6d

.github/workflows/benchmark.yml

@@ -0,0 +1,30 @@
+---
+name: Benchmarks
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+env:
+  COLUMNS: 120
+
+jobs:
+  benchmarks:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup rust toolchain, cache and cargo-codspeed binary
+        uses: moonrepo/setup-rust@v1
+        with:
+          channel: stable
+          cache-target: release
+          bins: cargo-codspeed
+      - name: Build the benchmark target(s)
+        run: cargo codspeed build
+      - name: Run the benchmarks
+        uses: CodSpeedHQ/action@v2
+        with:
+          run: cargo codspeed run
+          token: ${{ secrets.CODSPEED_TOKEN }}