fix: deadlink job

[laysakura]

Issue number and link

Fixes: #166

Describe your changes

Stop exporting pub structs/traits in top-level to prevent pest_derive to implement its traits.

See #166 why this fix works.

This is a breaking change since it changes import path of pub types.

Checklist before requesting a review

• I follow the Semantic Pull Requests rules (bugfix/feature)
• I specified links to related issues (must: bugfix, want: feature)
• I have performed a self-review of my code (bugfix/feature)
• I have added thorough tests (bugfix/feature)
• I have edited ## [Unreleased] section in CHANGELOG.md following keep a changelog syntax (bugfix/feature)
• I {made/will make} a related pull request for documentation repo (feature)

[laysakura]

lcov job started to fail: https://github.com/SpringQL/SpringQL/runs/6663137648?check_suite_focus=true

It seems to run rustdoc ... --test ... to gather coverage and fail in Address already in use.

This might be due to #156, which add a test case to use the same port as examples/doc_app1.rs.

[laysakura]

Close this PR.

• SpringEventDuration, SpringTimestamp, SpringValue become private since crate::api is private mod.
• After making crate::api public, SpringEventDuration again reported deadlink.