Update Action's README

Closes gh-22

.github/actions/auto-merge-forward/README.adoc

@@ -0,0 +1,52 @@
+= Auto Merge Forward
+
+This action is used to automatically merge forward commits between branches.
+
+Consider the following workflow configuration:
+
+[source,yaml]
+----
+name: Auto Merge Forward Dependabot Commits
+
+jobs:
+  auto-merge-forward-dependabot:
+    name: Auto Merge Forward Dependabot Commits
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        id: checkout
+        uses: actions/checkout@v4
+      - name: Setup GitHub User
+        id: setup-gh-user
+        run: |
+          git config user.name 'github-actions[bot]'
+          git config user.email 'github-actions[bot]@users.noreply.github.com'
+      - name: Run Auto Merge Forward
+        id: run-auto-merge-forward
+        uses: spring-io/spring-security-release-tools/.github/actions/auto-merge-forward@actions-v1
+        with:
+          branches: 5.8.x,6.1.x,6.2.x,main
+          from-author: dependabot[bot]
+----
+
+The action will do the following:
+
+1. Verify if there is any commit in the previous branch that is not present in the current branch by running `git log 5.8.x ^6.1.x --format=%an --no-merges`
+2. If a commit is found, the author of the commit is compared with the `from-author` input, if they don't match, skip to the next branches.
+   1. If there are multiple commits, all the authors must match the `from-author` input.
+3. A merge is done into the current branch by running `git merge 5.8.x -s ours` and the branch is selected for push.
+4. Push all the branches that had a merge by running `git push --atomic origin 6.1.x 6.2.x main`
+
+== Inputs
+
+- *from-author*: Only merge if all commits match the author. Defaults to `dependabot[bot]`
+- *use-author-email*: Whether to use author email to check if the author matches. Defaults to author name.
+- *branches* (required): The branches to merge, from oldest to newest, separated by a comma.
+- *merge-strategy*: The merge strategy to use. Defaults to `ours`.
+- *dry-run*: Whether to push the changes. Defaults to `false`.
+
+== Development
+
+Run `npm run bundle` to prepare the `dist` folder before pushing the changes.

.github/actions/generate-dependabot-yml/README.adoc

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+= Generate Dependabot YML
+
+This action facilitates the automatic update of a Dependabot configuration template file (dependabot.yml).
+This action reads a template file, resolves updates based on specified package ecosystems and target branches, and then writes the updated template to the `.github` directory within your repository.
+
+== Inputs
+
+The action accepts the following inputs:
+
+- *gradle-branches* (string): Comma-separated list of target branches for Gradle dependencies.
+- *github-actions-branches* (string): Comma-separated list of target branches for GitHub Actions dependencies.
+- *template-file* (string): Path to the Dependabot template file within the repository. Defaults to `.github/dependabot.template.yml`.
+
+== Output
+
+This action doesn't provide any output variables.
+
+== How it Works
+
+The action follows these steps:
+
+. Input Processing:
+.. Reads the specified template file.
+.. Parses the YAML content of the template file to extract update definitions.
+
+. Update Resolution:
+.. For each defined update in the template, it determines the package ecosystem.
+.. If the ecosystem is gradle, it resolves updates for each target branch specified in `gradle-branches`.
+.. If the ecosystem is github-actions, it resolves updates for each target branch specified in `github-actions-branches`.
+
+. Update Template:
+.. Updates the template file with the resolved updates.
+.. Dumps the updated template as YAML.
+.. Writes the updated Dependabot template to `.github/dependabot.yml`.
+
+. Error Handling:
+.. If any errors occur during the process, the action fails and sets an error message.
+
+== Example Usage
+
+[source,yaml]
+----
+name: Update dependabot.yml
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '0 0 * * *' # Once per day at midnight UTC
+
+permissions:
+  contents: read
+
+jobs:
+  main:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+      - uses: spring-io/spring-security-release-tools/.github/actions/generate-dependabot-yml@actions-v1
+        name: Update dependabot.yml
+        with:
+          gradle-branches: 5.8.x,6.1.x,6.2.x,main
+          github-actions-branches: 5.8.x,6.1.x,6.2.x,main,docs-build
+          gh-token: ${{ secrets.GITHUB_TOKEN }}
+      - uses: stefanzweifel/git-auto-commit-action@v5
+        with:
+          commit_message: Update dependabot.yml
+----
+
+== Development
+
+Run `npm run bundle` to prepare the `dist` folder before pushing the changes.