[ADD] general: new doc about in app purchases

general.rst

@@ -11,3 +11,4 @@ General
    general/unsplash
    general/base_import
    general/auth
+   general/in_app_purchase

general/in_app_purchase.rst

@@ -0,0 +1,8 @@
+===============
+In-App Purchase
+===============
+
+.. toctree::
+   :titlesonly:
+
+   in_app_purchase/in_app_purchase

general/in_app_purchase/in_app_purchase.rst

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+==================================================
+General guide about In-App Purchase (IAP) Services
+==================================================
+In-App Purchases (IAP) gives access to additional services through Odoo. For instance, it allows me to send SMS Text Messages or to send Invoices by post directly from my database.
+
+Buying Credits
+=========================================
+Each IAP Service relies on prepaid credits to work and has its own pricing. To consult my current balance or to recharge my account, go to *Settings> Odoo IAP > View my Services*.
+
+.. image:: media/image1.png
+   :align: center
+
+.. tip:: If I am on Odoo Online (SAAS) and have the Enterprise version, I benefit from free credits to test our IAP features.
+
+IAP accounts
+=========================================
+Credits to use IAP services are stored on IAP accounts, which are specific to each service and database. By default, IAP accounts are common to all companies, but can be restricted to specific ones by going to *Settings app > Activate the Developer Mode > Technical Settings > IAP Accoun*.
+
+.. image:: media/image2.png
+   :align: center
+   
+IAP Portal
+=========================================
+The IAP Portal is a platform regrouping my IAP Services. It is accessible from *Settings app > Odoo IAP > View my Services*. From there, I can view my current balance, recharge my credits, review my consumption and set a reminder to when credits are low.
+
+.. image:: media/image3.png
+   :align: center
+
+Get notified when credits are low
+=========================================
+To be notified when it’s time to recharge my credits, I’ll go to my IAP Portal through *Settings app> Odoo IAP > View my Services*, unfold a service and mark the Receive threshold warning option.
+Then, I’ll provide a minimum amount of credits and email addresses. Now, every time that the limit is reached, an automatic reminder will be sent to by email!
+
+.. image:: media/image4.png
+   :align: center
+
+IAP services available
+=========================================
+Different services are available depending on the hosting type of your Database:
+- *Odoo Online (SAAS)*: only the IAP services provided by Odoo can be used (i.e. the SMS, Snailmail, Reveal and Partner Autocomplete features);
+- *Odoo.sh and Odoo Enterprise (on-premise)*: both the services provided by Odoo and by third-party apps can be used.
+
+Offering my own services 
+=========================================
+I am more than welcome to offer my own IAP services through Odoo Apps! It is the perfect opportunity to get recurring revenue for an ongoing service use rather than — and possibly instead of — a sole initial purchase. Please, find more information at: `In-App Purchase <https://www.odoo.com/documentation/master/webservices/iap.html>`_