fix: handle 0 as fixed gas fee

[abhinavmsra]

Issue

For Free gas networks like GoQuorum, we need fixed_wei_value to be set to zero. However, the serializer check doesnt handle 0 for fixed types & raises APIException exception.

postgres=# select * from chains_gasprice;
-[ RECORD 1 ]------------+------------
id                       | 1
oracle_uri               | 
oracle_parameter         | 
gwei_factor              | 1.000000000
fixed_wei_value          | 0
rank                     | 100
chain_id                 | 
max_fee_per_gas          | 
max_priority_fee_per_gas | 

/api/v1/chains/:chainId/

{ "detail":"The gas price oracle or a fixed gas price was not provided for chain" }

Fix

This PR modifies the check to is not None to allow for zero values

/api/v1/chains/:chainId/

{
    ...,
    "gasPrice": [
       {
             "type": "fixed",
             "weiValue": "0"
        }
    ],
}

[coveralls]

Pull Request Test Coverage Report for Build 8715973662

Details

• 9 of 9 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 99.892%

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Totals
Change from base Build 8634197591:	0.3%
Covered Lines:	4606
Relevant Lines:	4611

---

💛 - Coveralls

[iamacook]

Thank you for the contribution, @abhinavmsra!

Other than missing a test case, all looks good to me. Can you add coverage in ChainGasPriceOracleTestCase? We can then get this merged and released.

[abhinavmsra]

@iamacook added tests as requested

[iamacook]

@iamacook added tests as requested

Thanks again, @abhinavmsra!