…n [feature/ig4-authentication] (mlrun#8674)

### 📝 Description
<!-- A short summary of what this PR does. -->
<!-- Include any relevant context or background information. -->
Fix an issue when running tests for the v4 Iguazio client.
Previously, instantiating the v4 client would initialize the real
iguazio.Client, which reads the local igz.yaml file and attempts to
refresh tokens. If this file exists on the machine, it could trigger
real network requests during tests.

This PR mocks the iguazio.Client using unittest.mock.MagicMock to
prevent actual initialization and external calls, allowing tests to run
safely in isolation.

---

### 🛠️ Changes Made
<!-- - Key changes (e.g., added feature X, refactored Y, fixed Z) -->

- Mocked `self._client` in the v4 client to avoid real Iguazio client
initialization.
- Updated the `iguazio_client` pytest fixture to apply the mock for v4
clients.

---

### ✅ Checklist
- [ ] I updated the documentation (if applicable)
- [x] I have tested the changes in this PR

---

### 🧪 Testing
<!-- - How it was tested (unit tests, manual, integration) -->  
<!-- - Any special cases covered. -->  

---

### 🔗 References
- Ticket link:
- Design docs links:
- External links:

---

### 🚨 Breaking Changes?

- [ ] Yes (explain below)
- [x] No

<!-- If yes, describe what needs to be changed downstream: -->

---

### 🔍️ Additional Notes
<!-- Anything else reviewers should know (follow-up tasks, known issues,
affected areas etc.). -->
<!-- ### 📸 Screenshots / Logs -->

### 📝 Description
<!-- A short summary of what this PR does. -->
<!-- Include any relevant context or background information. -->
This PR introduces support for MLRun authentication with IG4.
It rebases the `feature/ig4-authentication` branch onto `development`

This PR includes the following PRs:

1. #8345
2. #8370
3.  #8366
4. #8388
5. #8440
6. #8408
7. #8466
8. #8471
9. #8443
10. #8484
11. #8498
12. #8574
13. #8529
14. #8584
15. #8588
16. #8589
17. #8567
18. #8623
19. #8612
20. #8514
21. #8626
22. #8632
23. #8633
24. #8667
25. #8668
26. #8674
27. #8780
28. #8754
29. #8796
30. #8811
---

### 🛠️ Changes Made
<!-- - Key changes (e.g., added feature X, refactored Y, fixed Z) -->
To enable IG4 project authorization, set the following configs in mlrun
api:

```
MLRUN_HTTPDB__AUTHENTICATION__MODE: iguazio-v4
MLRUN_HTTPDB__AUTHENTICATION__IGUAZIO__SESSION_VERIFICATION_ENDPOINT: v1/identity/self
MLRUN_IGUAZIO_API_URL: http://igz-api:8000
```

Before importing MLRun, you must set:
```
MLRUN_AUTH_WITH_OAUTH_TOKEN__ENABLED=true
MLRUN_AUTH_TOKEN_ENDPOINT="https://igz-api.<namespace>.<system-domain>/api/v1/refresh-access-token"
```

---

### ✅ Checklist
- [x] I updated the documentation (if applicable)
- [x] I have tested the changes in this PR
- [ ] If I introduced a deprecation:
  - [ ] I followed the [Deprecation Guidelines](./DEPRECATION.md)
  - [ ] I updated the relevant Jira ticket for documentation

---

### 🧪 Testing
<!-- - How it was tested (unit tests, manual, integration) -->  
<!-- - Any special cases covered. -->  
Tested on IG4 system + unit tests

---

### 🔗 References
- Ticket link: https://iguazio.atlassian.net/browse/ML-9683,
https://iguazio.atlassian.net/browse/ML-9870,
https://iguazio.atlassian.net/browse/ML-9998
- Design docs links:
https://iguazio.atlassian.net/wiki/spaces/MLRUN/pages/399179866/Support+IG4+Authentication+in+MLRun+AuthVerifier+HLD,
https://iguazio.atlassian.net/wiki/spaces/MLRUN/pages/411960071/Support+sdk-side+IG4+authentication+-+token+usage+and+management+HLD,
https://iguazio.atlassian.net/wiki/spaces/MLRUN/pages/404521061/BE+Secret+Token+Support+HLD,
- External links:
https://iguazio.atlassian.net/wiki/spaces/ARC/pages/361103361/MLRun+Secret+Tokens+in+IG4

---

### 🚨 Breaking Changes?

- [x] Yes (explain below)
- [] No

Removed unused API endpoints `- POST /api/v1/user-secrets` which was not
in used

---

### 🔍️ Additional Notes


How to enable IG4 authentication -
https://iguazio.atlassian.net/wiki/spaces/PLAT/pages/457671097/Enable+IG4+Authentication+in+MLRun

---------

Co-authored-by: Katerina Molchanova <35141662+rokatyy@users.noreply.github.com>
Co-authored-by: Amit Elbaz <66309521+elbamit@users.noreply.github.com>