fix: onboarding sequence diagrams aligned with normative texts

[peppelinux]

this PR resolves #852

[Copilot]

Pull Request Overview

This PR aligns onboarding sequence diagrams with their corresponding normative texts by simplifying the federation onboarding process flow and correcting terminology inconsistencies throughout the Italian and English documentation.

Key changes:

• Simplified the federation onboarding sequence diagram by removing the /resolve endpoint interaction and streamlining the flow to focus on certificate issuance and subordinate statement fetching
• Standardized terminology by consistently capitalizing "Credenziali" (Credentials) and "Attributi" (Attributes) throughout Italian documentation
• Updated documentation version from 1.2.0 to 1.2.1

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/it/plantuml/federation-onboarding-process.puml	Simplified federation onboarding flow by removing resolve endpoint steps and focusing on direct subordinate statement retrieval
docs/it/onboarding-high-level.rst	Standardized capitalization of "Credenziali" and "Attributi" terms throughout the Italian documentation and updated PlantUML caption URLs
docs/it/conf.py	Updated documentation version to 1.2.1
docs/en/plantuml/federation-onboarding-process.puml	Applied same federation onboarding flow simplification as Italian version
docs/en/onboarding-high-level.rst	Updated PlantUML caption URL to match new diagram
docs/en/conf.py	Updated documentation version to 1.2.1

Comments suppressed due to low confidence (2)

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[Copilot]

[nitpick] The diagram title has been removed. Consider adding a descriptive title back to the diagram for better documentation clarity, such as @startuml Federation Entity Onboarding Process.

Suggested change

	@startuml
	@startuml Federation Entity Onboarding Process

[Copilot]

[nitpick] The preposition 'about' is awkward in this context. Consider using 'for' instead: 'Issue X.509 Certificates for Federation Entity Public Keys in CSRs' for better clarity.

Suggested change

	ta -> ta: Issue X.509 Certificates about\nFederation Entity Public Keys in CSRs
	ta -> ta: Issue X.509 Certificates for\nFederation Entity Public Keys in CSRs