Add Gandr text to speech integration (#563)

Co-authored-by: Gandr <contact@gandr.ai>

Author: AALG123

integrations/gandr.md

@@ -0,0 +1,100 @@
+---
+layout: integration
+name: Gandr
+description: Gandr Text-to-Speech component for Haystack.
+authors:
+    - name: Gandr
+      socials:
+        github: Gandr-AI
+pypi: https://pypi.org/project/gandr-haystack/
+repo: https://github.com/Gandr-AI/gandr-haystack
+type: Model Provider
+report_issue: https://github.com/Gandr-AI/gandr-haystack/issues
+logo: /logos/gandr.png
+version: Haystack 2.0
+toc: true
+---
+
+### **Table of Contents**
+- [Overview](#overview)
+- [Installation](#installation)
+- [Usage](#usage)
+- [Parameters](#parameters)
+- [Loading a saved pipeline](#loading-a-saved-pipeline)
+- [License](#license)
+
+## Overview
+
+[Gandr](https://gandr.ai) is a text-to-speech API. This integration adds a
+`GandrTTS` component that turns text into WAV audio inside a Haystack pipeline,
+and optionally writes it to disk.
+
+Six stock voices, output at 8 kHz to 24 kHz, and every render is watermarked.
+
+## Installation
+
+```bash
+pip install gandr-haystack
+```
+
+## Usage
+
+Set `GANDR_API_KEY` in your environment. Keys start with `gnd_`, and a free key
+with 100,000 characters is available at [gandr.ai](https://gandr.ai) without a
+card.
+
+```python
+from gandr_haystack import GandrTTS
+
+tts = GandrTTS(voice="gandr-mia")
+result = tts.run(text="Your appointment is confirmed for Tuesday at two fifteen.",
+                 path="out.wav")
+result["audio"]   # WAV bytes
+```
+
+In a pipeline:
+
+```python
+from haystack import Pipeline
+from gandr_haystack import GandrTTS
+
+pipe = Pipeline()
+pipe.add_component("tts", GandrTTS())
+pipe.run({"tts": {"text": "Hello from Haystack."}})
+```
+
+## Parameters
+
+| Parameter | Default | Notes |
+|---|---|---|
+| `api_key` | `Secret.from_env_var("GANDR_API_KEY")` | Keys start with `gnd_` |
+| `voice` | `gandr-mia` | Also `gandr-ava`, `gandr-jenny`, `gandr-dane`, `gandr-leo`, `gandr-lewis` |
+| `language` | `en` | ISO language code |
+| `sample_rate` | `24000` | One of 8000, 16000, 22050, 24000 |
+| `url` | `https://tts.gandr.ai/v1/tts/bytes` | Override to pin a region |
+| `timeout` | `60.0` | Seconds |
+
+`run()` returns `{"audio": bytes, "path": str | None}`.
+
+The API key is held as a Haystack `Secret` read from the environment, so a
+serialized pipeline never carries the token. An HTTP failure raises
+`RuntimeError` carrying the API's own status and message, so an authentication
+error and a quota error are distinguishable.
+
+## Loading a saved pipeline
+
+Haystack does not deserialize a third-party component unless its module is
+allowlisted:
+
+```python
+from haystack.core.serialization import allow_deserialization_module
+
+allow_deserialization_module("gandr_haystack.tts")
+```
+
+Or set `HAYSTACK_DESERIALIZATION_ALLOWLIST=gandr_haystack.tts`. Saving with
+`to_dict()` requires nothing.
+
+## License
+
+MIT.