feat(api): Expose uptime data as text via API (#758)

* Expose Raw Uptime Data via API

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Add Test for Raw Uptime Data API Endpoint

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Document Raw Uptime Data API Endpoint

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Fix Test after #759 Core Refactor

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Update Raw Data Content Type

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Support 30d Data from Raw Uptime Endpoint

Signed-off-by: James Hillyard <james.hillyard@payara.fish>

* Update README.md

* Update README.md

---------

Signed-off-by: James Hillyard <james.hillyard@payara.fish>
Co-authored-by: TwiN <twin@linux.com>

README.md

@@ -119,6 +119,7 @@ Have any feedback or questions? [Create a discussion](https://github.com/TwiN/ga
     - [Response time](#response-time)
       - [How to change the color thresholds of the response time badge](#how-to-change-the-color-thresholds-of-the-response-time-badge)
   - [API](#api)
+    - [Raw Data](#raw-data)
   - [Installing as binary](#installing-as-binary)
   - [High level design overview](#high-level-design-overview)
 
@@ -2404,6 +2405,23 @@ Gzip compression will be used if the `Accept-Encoding` HTTP header contains `gzi
 The API will return a JSON payload with the `Content-Type` response header set to `application/json`.
 No such header is required to query the API.
 
+#### Raw Data
+Gatus exposes the raw data for one of your monitored endpoints.
+This allows you to track and aggregate data in your own applications for monitored endpoints. For instance if you want to track uptime for a period longer than 7 days.
+
+##### Uptime
+The path to get raw uptime data for an endpoint is:
+```
+/api/v1/endpoints/{key}/uptimes/{duration}
+```
+Where:
+- `{duration}` is `30d` (alpha), `7d`, `24h` or `1h`
+- `{key}` has the pattern `<GROUP_NAME>_<ENDPOINT_NAME>` in which both variables have ` `, `/`, `_`, `,` and `.` replaced by `-`.
+
+For instance, if you want the raw uptime data for the last 24 hours from the endpoint `frontend` in the group `core`, the URL would look like this:
+```
+https://example.com/api/v1/endpoints/core_frontend/uptimes/24h
+```
 
 ### Installing as binary
 You can download Gatus as a binary using the following command: