SUBMARINE-1417. Retrieve SUBMARINE_AUTH_SECRET from environment variable instead of using hard-coded value

[laiyousin]

What is this PR for?

Retrieve SUBMARINE_AUTH_SECRET from environment variable instead of using hard-coded value

What type of PR is it?

Bug Fix

Todos

What is the Jira issue?

https://issues.apache.org/jira/browse/SUBMARINE-1417

How should this be tested?

Screenshots (if appropriate)

Questions:

• Do the license files need updating? No
• Are there breaking changes for older versions? No
• Does this need new documentation? No

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 43.71%. Comparing base (4e68894) to head (a6a1015).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1125 +/- ## ======================================= Coverage 43.71% 43.71% ======================================= Files 130 130 Lines 6320 6320 ======================================= Hits 2763 2763 Misses 3557 3557 ``` | [Flag](https://app.codecov.io/gh/apache/submarine/pull/1125/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache) | Coverage Δ | | |---|---|---| | [python-unit](https://app.codecov.io/gh/apache/submarine/pull/1125/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache) | `43.71% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache#carryforward-flags-in-the-pull-request-comment) to find out more.

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[cdmikechen]

@laiyousin @xunliu

submarine.auth.default.secret is not hard-coded and can be overridden by SUBMARINE_AUTH_DEFAULT_SECRET in the environment variable. Therefore, I think this PR still needs more consideration, and there are too many problems in CI that have not been solved, and it still needs the support of other fixes to merge.

Refer to the documentation https://submarine.apache.org/docs/designDocs/wip-designs/security-implementation#authentication for more authentication details.

[cdmikechen]

If there is no more to deal with this PR, I will revert this recently and fix the problem in CI first.