Adds initial README file

Adds a README file explaining the project, oAuth management, and infisical setup.

The oAuth management section describes the manual steps required to get a refresh token from Strava and how to use it.
The Infisical setup section explains how to set up the Infisical vault with the required variables.

README.md

@@ -1,3 +1,31 @@
 # Strava-API
 
 API used to communicate with my strava account, will be used as a display project
+
+## WIP and strava oAuth management
+Right now the oAuth management is a bit manual, I need to get the refresh token manually from strava website, then store it in Infisical vault (or env variable for testing).
+
+### Steps to get refresh token
+1. Go to this URL (replace client_id with your strava app client id, redirect_uri with your redirect uri, and scope with the scopes you need):
+```https://www.strava.com/oauth/authorize?client_id=181987&response_type=code&redirect_uri=https://louisemard.dev&approval_prompt=force&scope=read,activity:read_all
+```
+2. Authorize the application and you will be redirected to the redirect_uri with a code in the URL.
+3. Exchange the code for a refresh token by making a POST request to the Strava API:
+```
+POST https://www.strava.com/oauth/token
+Content-Type: application/x-www-form-urlencoded
+
+client_id=181987
+client_secret=YOUR_CLIENT_SECRET
+code=AUTHORIZATION_CODE
+grant_type=authorization_code
+```
+4. The response will contain the refresh token, which you can then store in your Infisical vault or as an environment variable.
+The `REFRESH_TOKEN` is then used by the application to get new access tokens when needed. It's linked to your Strava account and allows the application to access your data.
+
+## Infisical setup
+To use infisical you need to have the following variables in your vault (environment "dev"):
+- `INFISICAL_CLIENT_SECRET`: your infisical client secret
+- `INFISICAL_CLIENT_ID`: your infisical client id
+- `INFISICAL_URL`: Infisical url, mine is `https://vault.louisemard.dev`
+- `INFISICAL_PROJECT_ID`: Project where the secrets are stored, right now only one project is supported