String support find order by customer

[yjhsieh2022]

• update find_by_customer_id in list_orders endpoint at /service/routes.py
• add test_list_orders_by_customer_id at tests/test_routes.py

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.03 :tada:

Comparison is base (f51916d) 95.82% compared to head (9b56b92) 95.85%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #78 +/- ## ========================================== + Coverage 95.82% 95.85% +0.03% ========================================== Files 8 8 Lines 359 362 +3 ========================================== + Hits 344 347 +3 Misses 15 15 ``` | [Impacted Files](https://app.codecov.io/gh/CSCI-GA-2820-SU23-001/orders/pull/78?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CSCI-GA-2820-SU23-001) | Coverage Δ | | |---|---|---| | [service/routes.py](https://app.codecov.io/gh/CSCI-GA-2820-SU23-001/orders/pull/78?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CSCI-GA-2820-SU23-001#diff-c2VydmljZS9yb3V0ZXMucHk=) | `96.06% <100.00%> (+0.09%)` | :arrow_up: |

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