Fix foreign keys

[Tigrov]

• Fix multiple foreign keys referencing to one table
• Fix possible null columns for reference

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌
Fixed issues	-

[what-the-diff]

PR Summary

• Improved Foreign Key Handling
  Improved how our system handles foreign keys. Now, it can efficiently process multiple foreign keys from the same table. In the case where a specific parameter is undefined, it will smartly use primary key column names as the foreign key column names.

• Updated Test Cases
  A new test case has been added to ensure the correct functioning of the improved foreign key handling mechanism. This will help maintain high standards of system reliability and correctness.

• Added New Database Tables for Testing
  Enhanced the database used for testing by incorporating two new tables. These tables, 'foreign_keys_parent' and 'foreign_keys_child', will be significant in testing and ensuring the proper functioning of foreign keys for multiple tables.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.19% ⚠️

Comparison is base (aa85945) 98.21% compared to head (6f2ac76) 98.02%.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #268      +/-   ##
============================================
- Coverage     98.21%   98.02%   -0.19%     
- Complexity      325      328       +3     
============================================
  Files            17       17              
  Lines          1006     1013       +7     
============================================
+ Hits            988      993       +5     
- Misses           18       20       +2     

Files Changed	Coverage Δ
src/TableSchema.php	0.00% <ø> (-100.00%)	⬇️
src/Schema.php	100.00% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[vjik]

Should we mark TableSchema::compositeForeignKey() as deprecated and remove it in the next major version?

Seems, TableSchemaInterface::compositeForeignKey() used only here, and after merge of this PR can be marked as deprecated also.

[vjik]

See previous comment and need line in changelog also.

And several optional suggestions.