Create client registration spec draft ("Client Registration")

This is the specification (CDSC-WG1-02) describing how clients (e.g. companies wanting to request data from customers) can register with utility servers in to use the utility's offered capabilities (e.g. access to customer data via OAuth).

[x] Write summary overview with example
- Draft: https://github.com/daniel-utilityapi/Customer-Data/blob/main/website/specs/cdsc-wg1-02/overview.md
- Render: https://daniel-utilityapi.github.io/Customer-Data/specs/cdsc-wg1-02/overview
[x] Review summary overview and example with working group
[x] Write specification draft
- Source: https://github.com/daniel-utilityapi/Customer-Data/blob/issue_16_client_registration/specifications/cdsc-wg1-02.md
- Render: https://daniel-utilityapi.github.io/Customer-Data/specs/cdsc-wg1-02
[x] Open pull request for specification draft
[ ] Review pull request with working group
[ ] Update based on feedback
[ ] Merge when consensus is obtained

carbon-data-specification / Customer-Data

Create client registration spec draft ("Client Registration") #16