Store the policy JSON columns as TEXT for MySQL 5.6

The branch stored scopejson, desiredstate and params as sa.JSON, the only JSON
columns in the product. MySQL 5.6 has no JSON type - it arrived in 5.7 - and the
migration failed there with a bare syntax error near the word JSON.

They are TEXT now, through a JSONText type decorator, so the seventeen call sites
still assign and read dicts. The convention elsewhere is already TEXT:
guides.blocksjson, geenforce.manifestjson.

Spec regenerated: 331 paths, 477 operations across 22 surfaces.

plugins/computers/models/policy.py

@@ -18,6 +18,7 @@ every table for a clean rollback.
 """
 
 from shopdb.api import db, BaseModel
+from .jsontext import JSONText
 
 
 # Provenance of a policy row.
@@ -43,7 +44,7 @@ class ConfigurationPolicy(BaseModel):
     # Boolean target AST: {"type":"and","nodes":[{"type":"pctype","id":3},
     # {"type":"not","node":{"type":"app","id":12}}]}. Validated server-side
     # (known node types, depth cap) before it is stored - see policyscope.
-    scopejson = db.Column(db.JSON, nullable=True)
+    scopejson = db.Column(JSONText, nullable=True)
 
     # GE-Enforce interop seam (see POLICY_SOURCE_LOCAL).
     source = db.Column(db.String(50), default=POLICY_SOURCE_LOCAL, nullable=False)
@@ -101,11 +102,11 @@ class ConfigurationPolicyAction(BaseModel):
 
     # Desired-state target for mode=desired, as JSON so different actions can
     # express different targets (e.g. {"running": true}). Null for gate mode.
-    desiredstate = db.Column(db.JSON, nullable=True)
+    desiredstate = db.Column(JSONText, nullable=True)
 
     # Optional action parameters passed through to the command (JSON), and an
     # optional reconcile cadence in minutes (null = reconcile on every report).
-    params = db.Column(db.JSON, nullable=True)
+    params = db.Column(JSONText, nullable=True)
     intervalminutes = db.Column(db.Integer, nullable=True)
 
     sortorder = db.Column(db.Integer, default=0, nullable=False)