[ISSUE-2779] Add user in session

[flaneur2020]

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Summary

this PR adds a user record in the session, which recorded on the authenticate phase of mysql & clickhouse. it also adds a user field in the system.processes table.

Changelog

• Improvement

Related Issues

Fixes #2779

Test Plan

Unit Tests
Stateless Tests

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[BohuTANG]

it will be the UserInfo in the future not only a user name?

[flaneur2020]

I'm taking UserInfo at first but reverted it back to a simple user name, in the current code base UserInfo is a fat object:

  pub struct UserInfo {
      pub name: String,
      pub hostname: String,
      pub password: Vec<u8>,
      pub auth_type: AuthType,
      pub privileges: UserPrivilege,
      pub quota: UserQuota,
  }

the fields inside UserInfo might get mutated on the fly (like quota, privileges, even password), or mutated by another query instance. a conservative usage of UserInfo might be always fetching UserInfo from the metasrv, and make it transactional with the user-related operations.

in the case about session privilege, we can construct a unique identifier for the privilege grants by user_name + client_address.

[codecov-commenter]

Codecov Report

Merging #2986 (eeeb8cd) into main (f6a5903) will decrease coverage by 0%.
The diff coverage is 25%.

@@          Coverage Diff          @@
##            main   #2986   +/-   ##
=====================================
- Coverage     68%     68%   -1%     
=====================================
  Files        649     649           
  Lines      34018   34022    +4     
=====================================
  Hits       23181   23181           
- Misses     10837   10841    +4     

Impacted Files	Coverage Δ
query/src/sql/plan_parser_test.rs	100% <ø> (ø)
...src/datasources/database/system/processes_table.rs	33% <25%> (-1%)	⬇️
common/management/src/cluster/cluster_mgr.rs	80% <0%> (-1%)	⬇️
query/src/clusters/cluster.rs	54% <0%> (-1%)	⬇️
common/mem-allocator/src/malloc_size.rs	73% <0%> (+1%)	⬆️

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[BohuTANG]

It would be nice to add a unit test in test crate we have some MutableStatus tests there

[flaneur2020]

@BohuTANG thank you for remind, i've added a test case on the getter/setter for current user

[flaneur2020]

to test the behaviour of session's current user, i'd split another PR to add a current_user() function

[BohuTANG]

/lgtm

[databend-bot]

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