Configuration context alignment

Choose the appropriate configuration context based on how changes will be handled by the system. When defining custom configuration variables: 1. Use `PGC_POSTMASTER` for options that require a server restart or cannot be changed while the server is running

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Choose the appropriate configuration context based on how changes will be handled by the system. When defining custom configuration variables:

  1. Use PGC_POSTMASTER for options that require a server restart or cannot be changed while the server is running
  2. Use PGC_SIGHUP only when there is code to properly handle configuration changes at runtime
  3. Implement appropriate handler functions for configurations that need special processing when changed

Example of proper context selection:

DefineCustomStringVariable(
    "neon.safekeeper_extra_conninfo_options",
    "libpq keyword parameters and values to apply to safekeeper connections",
    NULL,
    &safekeeper_extra_conninfo_options,
    "",
    PGC_POSTMASTER,  // Requires restart since we don't have reconnection code
    ...
);

// For configurations that need special handling when changed:
DefineCustomStringVariable(
    "neon.safekeepers",
    "List of safekeepers",
    NULL,
    &safekeepers_list,
    "",
    PGC_SIGHUP,  // Can change during runtime
    ...
    NULL, assign_neon_safekeepers, NULL  // Custom handler function
);

Adding clear comments when configurations have special behavior enhances code maintainability.

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