BFD-4291: Update overshare_mbi logic

[aschey-forpeople]

JIRA Ticket:
BFD-4291

What Does This PR Do?

• Updates overshare logic to handle overshared MBIs based on recent findings related to IDR's merged process. There's a comment in the model explaining the details, but I'll paste it here for convenience:

The xref data in the bene_hstry table is not completely reliable
because sometimes HICNs can be reused, causing two records to be
xref'd even if they're not the same person.
We'll only trust xref records that have a valid entry in the bene_xref
table (this means it's coming from CME). For any MBIs tied to more than
one bene_sk that doesn't have a valid xref, we will prevent it from being
shown since it may be incorrectly linked to more than one person.

• Replaces the overshare_mbis materialized view with a separate table that will be loaded from IDR each time. Materialized views are not smart enough to perform incremental refreshes, so this approach is actually substantially faster.

• Refactors some of the larger Python functions in the pipeline to make the code a bit more readable.

What Should Reviewers Watch For?

If you're reviewing this PR, please check for these things in particular:

What Security Implications Does This PR Have?

Please indicate if this PR does any of the following:

• Adds any new software dependencies

• Modifies any security controls

• Adds new transmission or storage of data

• Any other changes that could possibly affect security?

• I have considered the above security implications as it relates to this PR. (If one or more of the above apply, it cannot be merged without the ISSO or team security engineer's (@sb-benohe) approval.)

• I have created tests to sufficiently ensure the reliability of my code, if applicable. If this is a modification to an existing piece of code, I have audited the associated tests to ensure everything works as expected.

Validation

Have you fully verified and tested these changes? Is the acceptance criteria met? Please provide reproducible testing instructions, code snippets, or screenshots as applicable.

[np-complete0]

return type should be int here:
def transform_null_int(value: int | None) -> float:
in model.py

[bfd-sast]

Quality Gate passed for 'bfd-parent'

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube