Add documentation for Repository Synchronization

- add install_gh_tool.md
- add install_tea_tool.md
- add synchronize-repositories.md

install-gh-tool.md

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+# Installation of gh (GitHub) CLI tool
+
+This tools is used to interact with GitHub via CLI to e.g. create PullRequests.
+
+## Prerequisits
+
+* ssh public-key for GitHub
+* [Personal Access Token](https://github.com/settings/token) (classic)
+    * Link: GitHub -> Developer Settings -> Personal Access Tokens -> Tokens (classic)
+    * Permissions: `admin:public_key, read:org, repo`
+
+## Installation of gh Tool on Debian / Ubuntu and co.
+
+Use the following bash snippet to get `gh` tool installed on your machine.
+
+```bash
+type -p curl >/dev/null || (sudo apt update && sudo apt install curl -y)
+curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg | sudo dd of=/usr/share/keyrings/githubcli-archive-keyring.gpg \
+&& sudo chmod go+r /usr/share/keyrings/githubcli-archive-keyring.gpg \
+&& echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/githubcli-archive-keyring.gpg] https://cli.github.com/packages stable main" | sudo tee /etc/apt/sources.list.d/github-cli.list > /dev/null \
+&& sudo apt update \
+&& sudo apt install gh -y
+```
+
+## Authentication with gh tool
+
+Run the following command to authenticate against Github
+
+```
+gh auth login
+```
+
+Fill in the following information and paste the Token. 
+
+![Alt-Text](_static/images/gh_auth_login.png)
+
+The tool gives access to your GitHub account.

install-tea-tool.md

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+# Installation of tea (Gitea) CLI tool
+
+This tool is used to interact with Gitea via CLI to e.g. create PullRequests.
+
+## Prerequisits
+
+* ssh public-key for Gitea
+* An [Access Token](https://gitea.eco.tsi-dev.otc-service.com/user/settings/applications)
+    * Gitea -> Settings -> Applications -> Manage Access Tokens -> \<Token-Name\> -> Generate Token
+
+## Installation
+
+Run the following command to get the `tea` tool and change permissions.
+```
+sudo wget https://dl.gitea.com/tea/0.9.2/tea-0.9.2-linux-amd64 -O /usr/local/bin/tea
+
+sudo chmod +x /usr/local/bin/tea
+```
+
+## Authentication with tea
+
+Run the following command to authenticate against our Gitea.
+
+```
+tea login add
+```
+
+Add the following information and your personal `Access Token`.
+
+![Alt-Text](_static/images/tea_login_add.png)

synchronize-repository.md

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+# Synchronize Repositories
+
+It is important to know to which git service the synchronization will happen. You need different CLI tools for either Gitea or GitHub.
+
+## Synchronize to GitHub
+
+Install the tools from prerequesits section and authenticate to GH to begin the synchronization.
+
+### Prerequisits
+
+* [Install `gh` tool](install-gh-tool.md)
+* Directory as workspace e.g. `~/workspace`
+
+### Synchronize from Gitea to GitHub
+
+Change directory to tools directory
+
+```bash
+cd ~/workspace/gitea/infra/otc-metadata/tools/
+```
+
+Run the following command to clone the prefered documentation of one service by selecting service-type and document-type. In our example: We clone the whole user manual from service CCE from internal (Gitea) to external (GitHub) repository. The option `--open-pr-gh` opens a Pull Request on GitHub side.
+
+```bash
+python sync_doc_repo.py --source-environment internal --target-environment public --service-type cce --document-type umn --branch-name main --work-dir ~/workspace/ --open-pr-gh
+```
+
+## Synchronize to Gitea
+
+Install the tools from prerequesits section and authenticate to Gitea to begin the synchronization.
+
+### Prerequisits
+
+* [Install `tea` tool](install-tea-tool.md)
+* Directory as workspace e.g. `~/workspace`
+
+
+### Synchronize from Gitea to GitHub
+
+Change directory to tools directory
+
+```bash
+cd ~/workspace/gitea/infra/otc-metadata/tools/
+```
+
+Run the following command to clone the prefered documentation of one service by selecting service-type and document-type. In our example: We clone the whole user manual from service Cloud Container Engine (cce) from external (GitHub) to internal (Gitea) repository.
+
+```bash
+python sync_doc_repo.py --source-environment public --target-environment internal --service-type cce --document-type umn --branch-name main --work-dir ~/workspace/
+```