Add following terms full_agonism, irreversible_agonism, voltage_dependent_gating_inhibition into CausalMechanismQualifierEnum

[Qi-ISB]

Question triggered this ticket:
There are inconsistencies between the Causal Mechanism mappings sheet for GtoPdb and the actual implementation or documentation of biolink . Following CausalMechanismQualifierEnum listed in the mappings sheet don't exist in the biolink documentation: full_agonism, irreversible_agonism, voltage_dependent_gating_inhibition

Reason:
@vdancik has reviewed these four terms and decide how to proceed (full_agonism, irreversible_agonism, voltage_dependent_gating_inhibition) and decided that they warrant inclusion in our enum. Thus here is a PR to add them into the CausalMechanismQualifierEnum.

[Qi-ISB]

Also, add qualifier: biochemical conversion / precursor for the following edge pair in SIGNOR:

subject: entity A
predicate: affects
object: entity B
object_aspect: abundance
object_direction: increased
mechanism: biochemical conversion / precursor

Reasoning from Matt:

One final question arose re: how to handle records where the "effect" is "upregulates quantity" and the "mechanism" is "precursor of". There are 664 of these in SIGNOR.

These records in the source data assert that Entity A upregulates quantity of Entity B - through the mechanism "precursor of" - because Entity A is converted in the cell to Entity B.

One way we can capture this is to say that Entity A derives_into Entity B (or, using the canonical predicate, Entity B derives_from Entity A). However, the fact that SIGNOR curators assert that A upregulates B may indicate that, in the cell, whenever A is present it will always lead to more of B being created. If this is the case, it may be useful to capture this in an edge using the upregulates SPOQ pattern. We should look into when SIGNOR uses the precursor mechanism?