New API Proposal Device_Volume_indicator.md

[NoelWirzius]

Field	Description
API family name	Device Data Volume
API family owner	Deutsche Telekom (Noel Wirzius)
API summary	This API offers detailed insights into the customer's data usage status, including whether they have remaining data volume available and their current position within that volume allocation. It accurately determines whether the customer is nearing the beginning or the end of their allocated data volume, providing valuable information for managing data usage efficiently.
Technical viability	The API should get information for a dedicated Sim-Card and also offer this in a subscription mode. The return value should not be a fixed value more an estimated indicator (e.g. <200mb, <1Gb ...)
Commercial viability	This API was requested by different content providers. It helps them to get more insights, how to deliver their traffic.
Validated in lab/productive environments?	Yes
Validated with operators?	Yes
Supporters in API Backlog Working Group	Vonage, Vodafone, Deutsche Telekom

[TEF-RicardoSerr]

A for last meeting (see minutes here) this PR can be merged