[FND-3] Release 7.0.0

[lucassus]

This pull request updates the README.md and various Python SDK files to improve documentation, fix typos, and update the SDK version from 6.1.0 to 7.0.0. It also introduces minor enhancements to API controllers and corrects some error-handling templates.

Documentation Updates:

• Updated SDK version references in README.md and Python SDK files from 6.1.0 to 7.0.0, including links to relevant documentation and examples. [1] [2] [3]
• Improved clarity and structure of API usage instructions in README.md, including new links to resources and integration examples.
• Fixed typos in method descriptions across multiple controllers (non-existant → non-existent, reposnse → response, subcription → subscription, reversable → reversible). [1] [2] [3] [4]

SDK Enhancements:

• Updated the user_agent method in base_controller.py to reflect the new SDK version, 7.0.0.
• Added consolidation_level as a query parameter in the list_invoices method to support more granular invoice filtering. [1] [2]

Error Handling Improvements:

• Enhanced error templates for 404 responses in coupons_controller.py and product_families_controller.py to include more detailed error messages. [1] [2]

Minor Additions:

• Added created_at and updated_at fields in the read_payment_profile method's example response.

Documentation Simplifications:

• Simplified the description of the record_payment_for_invoice method by removing redundant examples and focusing on its primary purpose.

[mykhi]

LGTM